diff --git a/ChangeLog.md b/ChangeLog.md new file mode 100644 --- /dev/null +++ b/ChangeLog.md @@ -0,0 +1,15 @@ +# 0.3.7.2 + +Stops Tag Soup from escaping &"<> which breaks HTML entities + +# 0.3.7.1 + +add max height and max width as valid style attributes + +# 0.3.7 + +clear the contents of style and script tags instead of escaping them + +# 0.3.5.6 + +expose safeTagName diff --git a/README.md b/README.md --- a/README.md +++ b/README.md @@ -1,5 +1,7 @@ # Summary +[![Tests](https://github.com/yesodweb/haskell-xss-sanitize/actions/workflows/tests.yml/badge.svg)](https://github.com/yesodweb/haskell-xss-sanitize/actions/workflows/tests.yml) + xss-sanitize allows you to accept html from untrusted sources by first filtering it through a white list. The white list filtering is fairly comprehensive, including support for css in style attributes, but there are limitations enumerated below. @@ -55,7 +57,7 @@ Ultimately this is where your security comes from. I would expect that a faulty white list would act as a strong deterrent, but this library strives for correctness. -The [source code of html5lib](http://code.google.com/p/html5lib/source/browse/python/html5lib/sanitizer.py) is the source of the white list and my implementation reference. If you feel a tag is missing from the white list, check to see if it has been added there. +The [source code of html5lib](https://github.com/html5lib/html5lib-python/blob/master/html5lib/filters/sanitizer.py) is the source of the white list and my implementation reference. If you feel a tag is missing from the white list, check to see if it has been added there. If anyone knows of better sources or thinks a particular tag/attribute/value may be vulnerable, please let me know. [HTML Purifier](http://htmlpurifier.org/live/smoketests/printDefinition.php) does have a more permissive and configurable (yet safe) white list if you are looking to add anything. diff --git a/Text/HTML/SanitizeXSS.hs b/Text/HTML/SanitizeXSS.hs deleted file mode 100644 --- a/Text/HTML/SanitizeXSS.hs +++ /dev/null @@ -1,266 +0,0 @@ -{-# LANGUAGE OverloadedStrings #-} --- | Sanatize HTML to prevent XSS attacks. --- --- See README.md for more details. -module Text.HTML.SanitizeXSS - ( - -- * Sanitize - sanitize - , sanitizeBalance - , sanitizeXSS - - -- * Custom filtering - , filterTags - , safeTags - , balanceTags - - -- * Utilities - , sanitizeAttribute - , sanitaryURI - ) where - -import Text.HTML.SanitizeXSS.Css - -import Text.HTML.TagSoup - -import Data.Set (Set(), member, notMember, (\\), fromList, fromAscList) -import Data.Char ( toLower ) -import Data.Text (Text) -import qualified Data.Text as T - -import Network.URI ( parseURIReference, URI (..), - isAllowedInURI, escapeURIString, uriScheme ) -import Codec.Binary.UTF8.String ( encodeString ) - -import qualified Data.Map as Map -import Data.Maybe (catMaybes) - - --- | Sanitize HTML to prevent XSS attacks. This is equivalent to @filterTags safeTags@. -sanitize :: Text -> Text -sanitize = sanitizeXSS - --- | alias of sanitize function -sanitizeXSS :: Text -> Text -sanitizeXSS = filterTags safeTags - --- | Sanitize HTML to prevent XSS attacks and also make sure the tags are balanced. --- This is equivalent to @filterTags (balanceTags . safeTags)@. -sanitizeBalance :: Text -> Text -sanitizeBalance = filterTags (balanceTags . safeTags) - --- | Filter which makes sure the tags are balanced. Use with 'filterTags' and 'safeTags' to create a custom filter. -balanceTags :: [Tag Text] -> [Tag Text] -balanceTags = balance Map.empty - --- | Parse the given text to a list of tags, apply the given filtering function, and render back to HTML. --- You can insert your own custom filtering but make sure you compose your filtering function with 'safeTags'! -filterTags :: ([Tag Text] -> [Tag Text]) -> Text -> Text -filterTags f = renderTagsOptions renderOptions { - optMinimize = \x -> x `member` voidElems -- converts to , converts to - } . f . canonicalizeTags . parseTags - -voidElems :: Set T.Text -voidElems = fromAscList $ T.words $ T.pack "area base br col command embed hr img input keygen link meta param source track wbr" - -balance :: Map.Map Text Int -> [Tag Text] -> [Tag Text] -balance m [] = - concatMap go $ Map.toList m - where - go (name, i) - | noClosing name = [] - | otherwise = replicate i $ TagClose name - noClosing = flip member voidElems -balance m (t@(TagClose name):tags) = - case Map.lookup name m of - Nothing -> TagOpen name [] : TagClose name : balance m tags - Just i -> - let m' = if i == 1 - then Map.delete name m - else Map.insert name (i - 1) m - in t : balance m' tags -balance m (TagOpen name as : tags) = - TagOpen name as : balance m' tags - where - m' = case Map.lookup name m of - Nothing -> Map.insert name 1 m - Just i -> Map.insert name (i + 1) m -balance m (t:ts) = t : balance m ts - --- | Filters out any usafe tags and attributes. Use with filterTags to create a custom filter. -safeTags :: [Tag Text] -> [Tag Text] -safeTags [] = [] -safeTags (t@(TagClose name):tags) - | safeTagName name = t : safeTags tags - | otherwise = safeTags tags -safeTags (TagOpen name attributes:tags) - | safeTagName name = TagOpen name - (catMaybes $ map sanitizeAttribute attributes) : safeTags tags - | otherwise = safeTags tags -safeTags (t:tags) = t:safeTags tags - -safeTagName :: Text -> Bool -safeTagName tagname = tagname `member` sanitaryTags - -safeAttribute :: (Text, Text) -> Bool -safeAttribute (name, value) = name `member` sanitaryAttributes && - (name `notMember` uri_attributes || sanitaryURI value) - --- | low-level API if you have your own HTML parser. Used by safeTags. -sanitizeAttribute :: (Text, Text) -> Maybe (Text, Text) -sanitizeAttribute ("style", value) = - let css = sanitizeCSS value - in if T.null css then Nothing else Just ("style", css) -sanitizeAttribute attr | safeAttribute attr = Just attr - | otherwise = Nothing - - --- | Returns @True@ if the specified URI is not a potential security risk. -sanitaryURI :: Text -> Bool -sanitaryURI u = - case parseURIReference (escapeURI $ T.unpack u) of - Just p -> (null (uriScheme p)) || - ((map toLower $ init $ uriScheme p) `member` safeURISchemes) - Nothing -> False - - --- | Escape unicode characters in a URI. Characters that are --- already valid in a URI, including % and ?, are left alone. -escapeURI :: String -> String -escapeURI = escapeURIString isAllowedInURI . encodeString - -safeURISchemes :: Set String -safeURISchemes = fromList acceptable_protocols - -sanitaryTags :: Set Text -sanitaryTags = fromList (acceptable_elements ++ mathml_elements ++ svg_elements) - \\ (fromList svg_allow_local_href) -- extra filtering not implemented - -sanitaryAttributes :: Set Text -sanitaryAttributes = fromList (allowed_html_uri_attributes ++ acceptable_attributes ++ mathml_attributes ++ svg_attributes) - \\ (fromList svg_attr_val_allows_ref) -- extra unescaping not implemented - -allowed_html_uri_attributes :: [Text] -allowed_html_uri_attributes = ["href", "src", "cite", "action", "longdesc"] - -uri_attributes :: Set Text -uri_attributes = fromList $ allowed_html_uri_attributes ++ ["xlink:href", "xml:base"] - -acceptable_elements :: [Text] -acceptable_elements = ["a", "abbr", "acronym", "address", "area", - "article", "aside", "audio", "b", "big", "blockquote", "br", "button", - "canvas", "caption", "center", "cite", "code", "col", "colgroup", - "command", "datagrid", "datalist", "dd", "del", "details", "dfn", - "dialog", "dir", "div", "dl", "dt", "em", "event-source", "fieldset", - "figcaption", "figure", "footer", "font", "form", "header", "h1", "h2", - "h3", "h4", "h5", "h6", "hr", "i", "img", "input", "ins", "keygen", - "kbd", "label", "legend", "li", "m", "main", "map", "menu", "meter", "multicol", - "nav", "nextid", "ol", "output", "optgroup", "option", "p", "pre", - "progress", "q", "s", "samp", "section", "select", "small", "sound", - "source", "spacer", "span", "strike", "strong", "sub", "sup", "table", - "tbody", "td", "textarea", "time", "tfoot", "th", "thead", "tr", "tt", - "u", "ul", "var", "video"] - -mathml_elements :: [Text] -mathml_elements = ["maction", "math", "merror", "mfrac", "mi", - "mmultiscripts", "mn", "mo", "mover", "mpadded", "mphantom", - "mprescripts", "mroot", "mrow", "mspace", "msqrt", "mstyle", "msub", - "msubsup", "msup", "mtable", "mtd", "mtext", "mtr", "munder", - "munderover", "none"] - --- this should include altGlyph I think -svg_elements :: [Text] -svg_elements = ["a", "animate", "animateColor", "animateMotion", - "animateTransform", "clipPath", "circle", "defs", "desc", "ellipse", - "font-face", "font-face-name", "font-face-src", "g", "glyph", "hkern", - "linearGradient", "line", "marker", "metadata", "missing-glyph", - "mpath", "path", "polygon", "polyline", "radialGradient", "rect", - "set", "stop", "svg", "switch", "text", "title", "tspan", "use"] - -acceptable_attributes :: [Text] -acceptable_attributes = ["abbr", "accept", "accept-charset", "accesskey", - "align", "alt", "autocomplete", "autofocus", "axis", - "background", "balance", "bgcolor", "bgproperties", "border", - "bordercolor", "bordercolordark", "bordercolorlight", "bottompadding", - "cellpadding", "cellspacing", "ch", "challenge", "char", "charoff", - "choff", "charset", "checked", "class", "clear", "color", - "cols", "colspan", "compact", "contenteditable", "controls", "coords", - -- "data", TODO: allow this with further filtering - "datafld", "datapagesize", "datasrc", "datetime", "default", - "delay", "dir", "disabled", "draggable", "dynsrc", "enctype", "end", - "face", "for", "form", "frame", "galleryimg", "gutter", "headers", - "height", "hidefocus", "hidden", "high", "hreflang", "hspace", - "icon", "id", "inputmode", "ismap", "keytype", "label", "leftspacing", - "lang", "list", "loop", "loopcount", "loopend", - "loopstart", "low", "lowsrc", "max", "maxlength", "media", "method", - "min", "multiple", "name", "nohref", "noshade", "nowrap", "open", - "optimum", "pattern", "ping", "point-size", "prompt", "pqg", - "radiogroup", "readonly", "rel", "repeat-max", "repeat-min", - "replace", "required", "rev", "rightspacing", "rows", "rowspan", - "rules", "scope", "selected", "shape", "size", "span", "start", - "step", - "style", -- gets further filtering - "summary", "suppress", "tabindex", "target", - "template", "title", "toppadding", "type", "unselectable", "usemap", - "urn", "valign", "value", "variable", "volume", "vspace", "vrml", - "width", "wrap", "xml:lang"] - -acceptable_protocols :: [String] -acceptable_protocols = [ "ed2k", "ftp", "http", "https", "irc", - "mailto", "news", "gopher", "nntp", "telnet", "webcal", - "xmpp", "callto", "feed", "urn", "aim", "rsync", "tag", - "ssh", "sftp", "rtsp", "afs" ] - -mathml_attributes :: [Text] -mathml_attributes = ["actiontype", "align", "columnalign", "columnalign", - "columnalign", "columnlines", "columnspacing", "columnspan", "depth", - "display", "displaystyle", "equalcolumns", "equalrows", "fence", - "fontstyle", "fontweight", "frame", "height", "linethickness", "lspace", - "mathbackground", "mathcolor", "mathvariant", "mathvariant", "maxsize", - "minsize", "other", "rowalign", "rowalign", "rowalign", "rowlines", - "rowspacing", "rowspan", "rspace", "scriptlevel", "selection", - "separator", "stretchy", "width", "width", "xlink:href", "xlink:show", - "xlink:type", "xmlns", "xmlns:xlink"] - -svg_attributes :: [Text] -svg_attributes = ["accent-height", "accumulate", "additive", "alphabetic", - "arabic-form", "ascent", "attributeName", "attributeType", - "baseProfile", "bbox", "begin", "by", "calcMode", "cap-height", - "class", "clip-path", "color", "color-rendering", "content", "cx", - "cy", "d", "dx", "dy", "descent", "display", "dur", "end", "fill", - "fill-opacity", "fill-rule", "font-family", "font-size", - "font-stretch", "font-style", "font-variant", "font-weight", "from", - "fx", "fy", "g1", "g2", "glyph-name", "gradientUnits", "hanging", - "height", "horiz-adv-x", "horiz-origin-x", "id", "ideographic", "k", - "keyPoints", "keySplines", "keyTimes", "lang", "marker-end", - "marker-mid", "marker-start", "markerHeight", "markerUnits", - "markerWidth", "mathematical", "max", "min", "name", "offset", - "opacity", "orient", "origin", "overline-position", - "overline-thickness", "panose-1", "path", "pathLength", "points", - "preserveAspectRatio", "r", "refX", "refY", "repeatCount", - "repeatDur", "requiredExtensions", "requiredFeatures", "restart", - "rotate", "rx", "ry", "slope", "stemh", "stemv", "stop-color", - "stop-opacity", "strikethrough-position", "strikethrough-thickness", - "stroke", "stroke-dasharray", "stroke-dashoffset", "stroke-linecap", - "stroke-linejoin", "stroke-miterlimit", "stroke-opacity", - "stroke-width", "systemLanguage", "target", "text-anchor", "to", - "transform", "type", "u1", "u2", "underline-position", - "underline-thickness", "unicode", "unicode-range", "units-per-em", - "values", "version", "viewBox", "visibility", "width", "widths", "x", - "x-height", "x1", "x2", "xlink:actuate", "xlink:arcrole", - "xlink:href", "xlink:role", "xlink:show", "xlink:title", "xlink:type", - "xml:base", "xml:lang", "xml:space", "xmlns", "xmlns:xlink", "y", - "y1", "y2", "zoomAndPan"] - --- the values for these need to be escaped -svg_attr_val_allows_ref :: [Text] -svg_attr_val_allows_ref = ["clip-path", "color-profile", "cursor", "fill", - "filter", "marker", "marker-start", "marker-mid", "marker-end", - "mask", "stroke"] - -svg_allow_local_href :: [Text] -svg_allow_local_href = ["altGlyph", "animate", "animateColor", - "animateMotion", "animateTransform", "cursor", "feImage", "filter", - "linearGradient", "pattern", "radialGradient", "textpath", "tref", - "set", "use"] - diff --git a/Text/HTML/SanitizeXSS/Css.hs b/Text/HTML/SanitizeXSS/Css.hs deleted file mode 100644 --- a/Text/HTML/SanitizeXSS/Css.hs +++ /dev/null @@ -1,140 +0,0 @@ -{-# LANGUAGE OverloadedStrings, CPP #-} -module Text.HTML.SanitizeXSS.Css ( - sanitizeCSS -#ifdef TEST -, allowedCssAttributeValue -#endif - ) where - -import Data.Text (Text) -import qualified Data.Text as T -import Data.Attoparsec.Text -import Data.Text.Lazy.Builder (toLazyText) -import Data.Text.Lazy (toStrict) -import Data.Set (member, fromList, Set) -import Data.Char (isDigit) -import Control.Applicative ((<|>), pure) -import Text.CSS.Render (renderAttrs) -import Text.CSS.Parse (parseAttrs) -import Prelude hiding (takeWhile) - --- import FileLocation (debug, debugM) - - --- this is a direct translation from sanitizer.py, except --- sanitizer.py filters out url(), but this is redundant -sanitizeCSS :: Text -> Text -sanitizeCSS css = toStrict . toLazyText . - renderAttrs . filter isSanitaryAttr . filterUrl $ parseAttributes - where - filterUrl :: [(Text,Text)] -> [(Text,Text)] - filterUrl = map filterUrlAttribute - where - filterUrlAttribute :: (Text, Text) -> (Text, Text) - filterUrlAttribute (prop,value) = - case parseOnly rejectUrl value of - Left _ -> (prop,value) - Right noUrl -> filterUrlAttribute (prop, noUrl) - - rejectUrl = do - pre <- manyTill anyChar (string "url") - skipMany space - _<-char '(' - skipWhile (/= ')') - _<-char ')' - rest <- takeText - return $ T.append (T.pack pre) rest - - - parseAttributes = case parseAttrs css of - Left _ -> [] - Right as -> as - - isSanitaryAttr (_, "") = False - isSanitaryAttr ("",_) = False - isSanitaryAttr (prop, value) - | prop `member` allowed_css_properties = True - | (T.takeWhile (/= '-') prop) `member` allowed_css_unit_properties && - all allowedCssAttributeValue (T.words value) = True - | prop `member` allowed_svg_properties = True - | otherwise = False - - allowed_css_unit_properties :: Set Text - allowed_css_unit_properties = fromList ["background","border","margin","padding"] - -allowedCssAttributeValue :: Text -> Bool -allowedCssAttributeValue val = - val `member` allowed_css_keywords || - case parseOnly allowedCssAttributeParser val of - Left _ -> False - Right b -> b - where - allowedCssAttributeParser = do - rgb <|> hex <|> rgb <|> cssUnit - - aToF = fromList "abcdef" - - hex = do - _ <- char '#' - hx <- takeText - return $ T.all (\c -> isDigit c || (c `member` aToF)) hx - - -- should have used sepBy (symbol ",") - rgb = do - _<- string "rgb(" - skipMany1 digit >> skipOk (== '%') - skip (== ',') - skipMany digit >> skipOk (== '%') - skip (== ',') - skipMany digit >> skipOk (== '%') - skip (== ')') - return True - - cssUnit = do - skip isDigit - skipOk isDigit - skipOk (== '.') - skipOk isDigit >> skipOk isDigit - skipSpace - unit <- takeText - return $ T.null unit || unit `member` allowed_css_attribute_value_units - -skipOk :: (Char -> Bool) -> Parser () -skipOk p = skip p <|> pure () - -allowed_css_attribute_value_units :: Set Text -allowed_css_attribute_value_units = fromList - [ "cm", "em", "ex", "in", "mm", "pc", "pt", "px", "%", ",", "\\"] - -allowed_css_properties :: Set Text -allowed_css_properties = fromList acceptable_css_properties - where - acceptable_css_properties = ["azimuth", "background-color", - "border-bottom-color", "border-collapse", "border-color", - "border-left-color", "border-right-color", "border-top-color", "clear", - "color", "cursor", "direction", "display", "elevation", "float", "font", - "font-family", "font-size", "font-style", "font-variant", "font-weight", - "height", "letter-spacing", "line-height", "overflow", "pause", - "pause-after", "pause-before", "pitch", "pitch-range", "richness", - "speak", "speak-header", "speak-numeral", "speak-punctuation", - "speech-rate", "stress", "text-align", "text-decoration", "text-indent", - "unicode-bidi", "vertical-align", "voice-family", "volume", - "white-space", "width"] - -allowed_css_keywords :: Set Text -allowed_css_keywords = fromList acceptable_css_keywords - where - acceptable_css_keywords = ["auto", "aqua", "black", "block", "blue", - "bold", "both", "bottom", "brown", "center", "collapse", "dashed", - "dotted", "fuchsia", "gray", "green", "!important", "italic", "left", - "lime", "maroon", "medium", "none", "navy", "normal", "nowrap", "olive", - "pointer", "purple", "red", "right", "solid", "silver", "teal", "top", - "transparent", "underline", "white", "yellow"] - --- used in css filtering -allowed_svg_properties :: Set Text -allowed_svg_properties = fromList acceptable_svg_properties - where - acceptable_svg_properties = [ "fill", "fill-opacity", "fill-rule", - "stroke", "stroke-width", "stroke-linecap", "stroke-linejoin", - "stroke-opacity"] diff --git a/src/Text/HTML/SanitizeXSS.hs b/src/Text/HTML/SanitizeXSS.hs new file mode 100644 --- /dev/null +++ b/src/Text/HTML/SanitizeXSS.hs @@ -0,0 +1,311 @@ +{-# LANGUAGE OverloadedStrings #-} +-- | Sanatize HTML to prevent XSS attacks. +-- +-- See README.md for more details. +module Text.HTML.SanitizeXSS + ( + -- * Sanitize + sanitize + , sanitizeBalance + , sanitizeXSS + + -- * Custom filtering + , filterTags + , safeTags + , safeTagsCustom + , clearTags + , clearTagsCustom + , balanceTags + + -- * Utilities + , safeTagName + , sanitizeAttribute + , sanitaryURI + ) where + +import Text.HTML.SanitizeXSS.Css + +import Text.HTML.TagSoup + +import Data.Set (Set(), member, notMember, (\\), fromList, fromAscList) +import Data.Char ( toLower ) +import Data.Text (Text) +import qualified Data.Text as T + +import Network.URI ( parseURIReference, URI (..), + isAllowedInURI, escapeURIString, uriScheme ) +import Codec.Binary.UTF8.String ( encodeString ) + +import Data.Maybe (mapMaybe) + + +-- | Sanitize HTML to prevent XSS attacks. This is equivalent to @filterTags safeTags@. +sanitize :: Text -> Text +sanitize = sanitizeXSS + +-- | alias of sanitize function +sanitizeXSS :: Text -> Text +sanitizeXSS = filterTags (safeTags . clearTags) + +-- | Sanitize HTML to prevent XSS attacks and also make sure the tags are balanced. +-- This is equivalent to @filterTags (balanceTags . safeTags)@. +sanitizeBalance :: Text -> Text +sanitizeBalance = filterTags (balanceTags . safeTags . clearTags) + +-- | Filter which makes sure the tags are balanced. Use with 'filterTags' and 'safeTags' to create a custom filter. +balanceTags :: [Tag Text] -> [Tag Text] +balanceTags = balance [] + +-- | Parse the given text to a list of tags, apply the given filtering +-- function, and render back to HTML. You can insert your own custom +-- filtering, but make sure you compose your filtering function with +-- 'safeTags' and 'clearTags' or 'safeTagsCustom' and 'clearTagsCustom'. +filterTags :: ([Tag Text] -> [Tag Text]) -> Text -> Text +filterTags f = renderTagsOptions renderOptions { + optEscape = id -- stops &"<> from being escaped which breaks existing HTML entities + , optMinimize = \x -> x `member` voidElems -- converts to , converts to + } . f . canonicalizeTags . parseTagsOptions (parseOptionsEntities (const Nothing)) + +voidElems :: Set T.Text +voidElems = fromAscList $ T.words $ T.pack "area base br col command embed hr img input keygen link meta param source track wbr" + +balance :: [Text] -- ^ unclosed tags + -> [Tag Text] -> [Tag Text] +balance unclosed [] = map TagClose $ filter (`notMember` voidElems) unclosed +balance (x:xs) tags'@(TagClose name:tags) + | x == name = TagClose name : balance xs tags + | x `member` voidElems = balance xs tags' + | otherwise = TagOpen name [] : TagClose name : balance (x:xs) tags +balance unclosed (TagOpen name as : tags) = + TagOpen name as : balance (name : unclosed) tags +balance unclosed (t:ts) = t : balance unclosed ts + +-- | Filters out unsafe tags and sanitizes attributes. Use with +-- filterTags to create a custom filter. +safeTags :: [Tag Text] -> [Tag Text] +safeTags = safeTagsCustom safeTagName sanitizeAttribute + +-- | Filters out unsafe tags and sanitizes attributes, like +-- 'safeTags', but uses custom functions for determining which tags +-- are safe and for sanitizing attributes. This allows you to add or +-- remove specific tags or attributes on the white list, or to use +-- your own white list. +-- +-- @safeTagsCustom safeTagName sanitizeAttribute@ is equivalent to +-- 'safeTags'. +-- +-- @since 0.3.6 +safeTagsCustom :: + (Text -> Bool) -- ^ Select safe tags, like + -- 'safeTagName' + -> ((Text, Text) -> Maybe (Text, Text)) -- ^ Sanitize attributes, + -- like 'sanitizeAttribute' + -> [Tag Text] -> [Tag Text] +safeTagsCustom _ _ [] = [] +safeTagsCustom safeName sanitizeAttr (t@(TagClose name):tags) + | safeName name = t : safeTagsCustom safeName sanitizeAttr tags + | otherwise = safeTagsCustom safeName sanitizeAttr tags +safeTagsCustom safeName sanitizeAttr (TagOpen name attributes:tags) + | safeName name = TagOpen name (mapMaybe sanitizeAttr attributes) : + safeTagsCustom safeName sanitizeAttr tags + | otherwise = safeTagsCustom safeName sanitizeAttr tags +safeTagsCustom n a (t:tags) = t : safeTagsCustom n a tags + +-- | Directly removes tags even if they are not closed properly. +-- This is importent to clear out both the script and iframe tag +-- in sequences like "