漏洞说明：
跨站脚本攻击(Cross Site Scripting)，为了不和层叠样式表(Cascading Style Sheets, CSS)的缩写混淆，故将跨站脚本攻击缩写为XSS。恶意攻击者往Web页面里插入恶意Web脚本代码（html、javascript、css等），当用户浏览该页面时，嵌入其中的Web脚本代码会被执行，从而达到恶意攻击用户的特殊目的。
测试步骤
访问系统网站，点击基础报告库进行编辑，使用Burp抓包并重新构造数据包.
重新访问，成功触发了XSS弹窗
解决方法：
将危险内容过滤去除，用HTML转义字符串（Escape Sequence）表达的则保留
添加脚本过滤类
/// <summary>/// Html 脚本过滤/// </summary>public class NHtmlFilter{protected static readonly RegexOptions REGEX_FLAGS_SI = RegexOptions.IgnoreCase | RegexOptions.Singleline | RegexOptions.Compiled;private static string P_COMMENTS = "<!--(.*?)-->";private static Regex P_COMMENT = new Regex("^!--(.*)--$", REGEX_FLAGS_SI);private static string P_TAGS = "<(.*?)>";private static Regex P_END_TAG = new Regex("^/([a-z0-9]+)", REGEX_FLAGS_SI);private static Regex P_START_TAG = new Regex("^([a-z0-9]+)(.*?)(/?)$", REGEX_FLAGS_SI);private static Regex P_QUOTED_ATTRIBUTES = new Regex("([a-z0-9|(a-z0-9\\-a-z0-9)]+)=([\"'])(.*?)\\2", REGEX_FLAGS_SI);private static Regex P_UNQUOTED_ATTRIBUTES = new Regex("([a-z0-9]+)(=)([^\"\\s']+)", REGEX_FLAGS_SI);private static Regex P_PROTOCOL = new Regex("^([^:]+):", REGEX_FLAGS_SI);private static Regex P_ENTITY = new Regex("&#(\\d+);?");private static Regex P_ENTITY_UNICODE = new Regex("&#x([0-9a-f]+);?");private static Regex P_ENCODE = new Regex("%([0-9a-f]{2});?");private static Regex P_VALID_ENTITIES = new Regex("&([^&;]*)(?=(;|&|$))");private static Regex P_VALID_QUOTES = new Regex("(>|^)([^<]+?)(<|$)", RegexOptions.Singleline | RegexOptions.Compiled);private static string P_END_ARROW = "^>";private static string P_BODY_TO_END = "<([^>]*?)(?=<|$)";private static string P_XML_CONTENT = "(^|>)([^<]*?)(?=>)";private static string P_STRAY_LEFT_ARROW = "<([^>]*?)(?=<|$)";private static string P_STRAY_RIGHT_ARROW = "(^|>)([^<]*?)(?=>)";private static string P_AMP = "&";private static string P_QUOTE = "\"";private static string P_LEFT_ARROW = "<";private static string P_RIGHT_ARROW = ">";private static string P_BOTH_ARROWS = "<>";// @xxx could grow large... maybe use sesat's ReferenceMapprivate static Dictionary<string, string> P_REMOVE_PAIR_BLANKS = new Dictionary<string, string>();private static Dictionary<string, string> P_REMOVE_SELF_BLANKS = new Dictionary<string, string>();/*** flag determining whether to try to make tags when presented with "unbalanced"* angle brackets (e.g. "<b text </b>" becomes "<b> text </b>"). If set to false,* unbalanced angle brackets will be html escaped.*/protected static bool alwaysMakeTags = true;/*** flag determing whether comments are allowed in input String.*/protected static bool stripComment = true;/// <summary>/// 不允许/// </summary>private string[] vDisallowed { get; set; }/// <summary>/// 允许/// </summary>protected Dictionary<string, List<string>> vAllowed { get; set; }/** counts of open tags for each (allowable) html element **/protected Dictionary<string, int> vTagCounts;/** html elements which must always be self-closing (e.g. "<img />") **/protected string[] vSelfClosingTags;/** html elements which must always have separate opening and closing tags (e.g. "<b></b>") **/protected string[] vNeedClosingTags;/** attributes which should be checked for valid protocols **/protected string[] vProtocolAtts;/** allowed protocols **/protected string[] vAllowedProtocols;/** tags which should be removed if they contain no content (e.g. "<b></b>" or "<b />") **/protected string[] vRemoveBlanks;/** entities allowed within html markup **/protected string[] vAllowedEntities;/// <summary>/// 是否为调试/// </summary>protected bool vDebug;public NHtmlFilter() : this(false) { }public NHtmlFilter(bool debug){//List<Item> vAllowed = new List<Item>();vAllowed = new Dictionary<string, List<string>>();#region 允许通过数组vAllowed.Add("a", new List<string>() { "target", "href", "title", "class", "style" });vAllowed.Add("addr", new List<string>() { "title", "class", "style" });vAllowed.Add("address", new List<string>() { "class", "style" });vAllowed.Add("area", new List<string>() { "shape", "coords", "href", "alt" });vAllowed.Add("article", new List<string>() { });vAllowed.Add("aside", new List<string>() { });vAllowed.Add("audio", new List<string>() { "autoplay", "controls", "loop", "preload", "src", "class", "style" });vAllowed.Add("b", new List<string>() { "class", "style" });vAllowed.Add("bdi", new List<string>() { "dir" });vAllowed.Add("bdo", new List<string>() { "dir" });vAllowed.Add("big", new List<string>() { });vAllowed.Add("blockquote", new List<string>() { "cite", "class", "style" });vAllowed.Add("br", new List<string>() { });vAllowed.Add("caption", new List<string>() { "class", "style" });vAllowed.Add("center", new List<string>() { });vAllowed.Add("cite", new List<string>() { });vAllowed.Add("code", new List<string>() { "class", "style" });vAllowed.Add("col", new List<string>() { "align", "valign", "span", "width", "class", "style" });vAllowed.Add("colgroup", new List<string>() { "align", "valign", "span", "width", "class", "style" });vAllowed.Add("dd", new List<string>() { "class", "style" });vAllowed.Add("del", new List<string>() { "datetime" });vAllowed.Add("details", new List<string>() { "open" });vAllowed.Add("div", new List<string>() { "class", "style" });vAllowed.Add("dl", new List<string>() { "class", "style" });vAllowed.Add("dt", new List<string>() { "class", "style" });vAllowed.Add("em", new List<string>() { "class", "style" });vAllowed.Add("font", new List<string>() { "color", "size", "face" });vAllowed.Add("footer", new List<string>() { });vAllowed.Add("h1", new List<string>() { "class", "style" });vAllowed.Add("h2", new List<string>() { "class", "style" });vAllowed.Add("h3", new List<string>() { "class", "style" });vAllowed.Add("h4", new List<string>() { "class", "style" });vAllowed.Add("h5", new List<string>() { "class", "style" });vAllowed.Add("h6", new List<string>() { "class", "style" });vAllowed.Add("header", new List<string>() { });vAllowed.Add("hr", new List<string>() { });vAllowed.Add("i", new List<string>() { "class", "style" });vAllowed.Add("img", new List<string>() { "src", "alt", "title", "style", "width", "height", "id", "_src", "loadingclass", "class", "data-latex", "data-id", "data-type", "data-s" });vAllowed.Add("ins", new List<string>() { "datetime" });vAllowed.Add("li", new List<string>() { "class", "style" });vAllowed.Add("mark", new List<string>() { });vAllowed.Add("nav", new List<string>() { });vAllowed.Add("ol", new List<string>() { "class", "style" });vAllowed.Add("p", new List<string>() { "class", "style" });vAllowed.Add("pre", new List<string>() { "class", "style" });vAllowed.Add("s", new List<string>() { });vAllowed.Add("section", new List<string>() { });vAllowed.Add("small", new List<string>() { });vAllowed.Add("span", new List<string>() { "class", "style" });vAllowed.Add("sub", new List<string>() { "class", "style" });vAllowed.Add("sup", new List<string>() { "class", "style" });vAllowed.Add("strong", new List<string>() { "class", "style" });vAllowed.Add("table", new List<string>() { "width", "border", "align", "valign", "class", "style" });vAllowed.Add("tbody", new List<string>() { "align", "valign", "class", "style" });vAllowed.Add("td", new List<string>() { "width", "rowspan", "colspan", "align", "valign", "class", "style" });vAllowed.Add("tfoot", new List<string>() { "align", "valign", "class", "style" });vAllowed.Add("th", new List<string>() { "width", "rowspan", "colspan", "align", "valign", "class", "style" });vAllowed.Add("thead", new List<string>() { "align", "valign", "class", "style" });vAllowed.Add("tr", new List<string>() { "rowspan", "align", "valign", "class", "style" });vAllowed.Add("tt", new List<string>() { });vAllowed.Add("u", new List<string>() { });vAllowed.Add("ul", new List<string>() { "class", "style" });vAllowed.Add("video", new List<string>() { "autoplay", "controls", "loop", "preload", "src", "height", "width", "class", "style" });#endregionvDebug = debug;vTagCounts = new Dictionary<string, int>();vSelfClosingTags = new string[] { "img" };vNeedClosingTags = new string[] { "a", "b", "strong", "i", "em" };vDisallowed = new string[] { "script" };vAllowedProtocols = new string[] { "http", "mailto" }; // no ftp.vProtocolAtts = new string[] { "src", "href" };vRemoveBlanks = new string[] { "a", "b", "strong", "i", "em" };vAllowedEntities = new string[] { "amp", "gt", "lt", "quot" };stripComment = true;alwaysMakeTags = true;}protected void reset(){vTagCounts = new Dictionary<string, int>();}protected void debug(string msg){if (vDebug)System.Diagnostics.Debug.WriteLine(msg);}//---------------------------------------------------------------// my versions of some PHP library functionspublic static string chr(int dec){return "" + (char)dec;}/// <summary>/// 转换成实体字符/// </summary>/// <param name="str"></param>/// <returns></returns>public static string htmlSpecialChars(string str){str = str.Replace(P_QUOTE, "\"");str = str.Replace(P_LEFT_ARROW, "<");str = str.Replace(P_RIGHT_ARROW, ">");str = str.Replace("\n", "<br>");return str;}//---------------------------------------------------------------/*** given a user submitted input String, filter out any invalid or restricted* html.** @param input text (i.e. submitted by a user) than may contain html* @return "clean" version of input, with only valid, whitelisted html elements allowed*/public string filter(string input){reset();string s = input;debug("************************************************");debug(" INPUT: " + input);s = escapeComments(s);debug(" escapeComments: " + s);s = balanceHTML(s);debug(" balanceHTML: " + s);s = checkTags(s);debug(" checkTags: " + s);s = processRemoveBlanks(s);debug("processRemoveBlanks: " + s);s = validateEntities(s);debug(" validateEntites: " + s);debug("************************************************\n\n");return s;}protected string escapeComments(string s){return Regex.Replace(s, P_COMMENTS, new MatchEvaluator(ConverMatchComments), RegexOptions.Singleline);}protected string regexReplace(string regex_pattern, string replacement, string s){return Regex.Replace(s, regex_pattern, replacement);}protected string balanceHTML(string s){if (alwaysMakeTags){//// try and form html//s = regexReplace(P_END_ARROW, "", s);s = regexReplace(P_BODY_TO_END, "<$1>", s);s = regexReplace(P_XML_CONTENT, "$1<$2", s);}else{//// escape stray brackets//s = regexReplace(P_STRAY_LEFT_ARROW, "<$1", s);s = regexReplace(P_STRAY_RIGHT_ARROW, "$1$2><", s);//// the last regexp causes '<>' entities to appear// (we need to do a lookahead assertion so that the last bracket can// be used in the next pass of the regexp)//s = s.Replace(P_BOTH_ARROWS, "");}return s;}protected string checkTags(string s){//替换不允许标签foreach (var item in vDisallowed){s = Regex.Replace(s, string.Format(@"<{0}\b(.)*?>(.)+?</{0}>", item), "");}s = Regex.Replace(s, P_TAGS, new MatchEvaluator(ConverMatchTags), RegexOptions.Singleline);// these get tallied in processTag// (remember to reset before subsequent calls to filter method)foreach (string key in vTagCounts.Keys){for (int ii = 0; ii < vTagCounts[key]; ii++){s += "</" + key + ">";}}return s;}protected string processRemoveBlanks(string s){foreach (string tag in vRemoveBlanks){s = regexReplace("<" + tag + "(\\s[^>]*)?></" + tag + ">", "", s);s = regexReplace("<" + tag + "(\\s[^>]*)?/>", "", s);}return s;}private string processTag(string s){// ending tagsMatch m = P_END_TAG.Match(s);if (m.Success){string name = m.Groups[1].Value.ToLower();if (allowed(name)){if (!inArray(name, vSelfClosingTags)){if (vTagCounts.ContainsKey(name)){vTagCounts[name] = vTagCounts[name] - 1;return "</" + name + ">";}}}}// starting tagsm = P_START_TAG.Match(s);if (m.Success){string name = m.Groups[1].Value.ToLower();string body = m.Groups[2].Value;string ending = m.Groups[3].Value;//debug( "in a starting tag, name='" + name + "'; body='" + body + "'; ending='" + ending + "'" );if (allowed(name)){string params1 = "";MatchCollection m2 = P_QUOTED_ATTRIBUTES.Matches(body);MatchCollection m3 = P_UNQUOTED_ATTRIBUTES.Matches(body);List<string> paramNames = new List<string>();List<string> paramValues = new List<string>();foreach (Match match in m2){paramNames.Add(match.Groups[1].Value); //([a-z0-9]+)paramValues.Add(match.Groups[3].Value); //(.*?)}foreach (Match match in m3){paramNames.Add(match.Groups[1].Value); //([a-z0-9]+)paramValues.Add(match.Groups[3].Value); //([^\"\\s']+)}string paramName, paramValue;for (int ii = 0; ii < paramNames.Count; ii++){paramName = paramNames[ii].ToLower();paramValue = paramValues[ii];if (allowedAttribute(name, paramName)){if (inArray(paramName, vProtocolAtts)){paramValue = processParamProtocol(paramValue);}params1 += " " + paramName + "=\"" + paramValue + "\"";}}if (inArray(name, vSelfClosingTags)){ending = " /";}if (inArray(name, vNeedClosingTags)){ending = "";}if (ending == null || ending.Length < 1){if (vTagCounts.ContainsKey(name)){vTagCounts[name] = vTagCounts[name] + 1;}else{vTagCounts.Add(name, 1);}}else{ending = " /";}return "<" + name + params1 + ending + ">";}else{return "";}}// commentsm = P_COMMENT.Match(s);if (!stripComment && m.Success){return "<" + m.Value + ">";}return "";}private string processParamProtocol(string s){s = decodeEntities(s);Match m = P_PROTOCOL.Match(s);if (m.Success){string protocol = m.Groups[1].Value;if (!inArray(protocol, vAllowedProtocols)){// bad protocol, turn into local anchor link insteads = "#" + s.Substring(protocol.Length + 1, s.Length - protocol.Length - 1);if (s.StartsWith("#//")){s = "#" + s.Substring(3, s.Length - 3);}}}return s;}private string decodeEntities(string s){s = P_ENTITY.Replace(s, new MatchEvaluator(ConverMatchEntity));s = P_ENTITY_UNICODE.Replace(s, new MatchEvaluator(ConverMatchEntityUnicode));s = P_ENCODE.Replace(s, new MatchEvaluator(ConverMatchEntityUnicode));s = validateEntities(s);return s;}private string validateEntities(string s){s = P_VALID_ENTITIES.Replace(s, new MatchEvaluator(ConverMatchValidEntities));s = P_VALID_QUOTES.Replace(s, new MatchEvaluator(ConverMatchValidQuotes));return s;}private static bool inArray(string s, string[] array){foreach (string item in array){if (item != null && item.Equals(s)){return true;}}return false;}private bool allowed(string name){return (vAllowed.Count == 0 || vAllowed.ContainsKey(name)) && !inArray(name, vDisallowed);}private bool allowedAttribute(string name, string paramName){return allowed(name) && (vAllowed.Count == 0 || vAllowed[name].Contains(paramName));}private string checkEntity(string preamble, string term){return ";".Equals(term) && isValidEntity(preamble)? '&' + preamble: "&" + preamble;}private bool isValidEntity(string entity){return inArray(entity, vAllowedEntities);}private static string ConverMatchComments(Match match){string matchValue = "<!--" + htmlSpecialChars(match.Groups[1].Value) + "-->";return matchValue;}private string ConverMatchTags(Match match){string matchValue = processTag(match.Groups[1].Value);return matchValue;}private string ConverMatchEntity(Match match){string v = match.Groups[1].Value;int decimal1 = int.Parse(v);return chr(decimal1);}private string ConverMatchEntityUnicode(Match match){string v = match.Groups[1].Value;int decimal1 = Convert.ToInt32("0x" + v, 16);return chr(decimal1);}private string ConverMatchValidEntities(Match match){string one = match.Groups[1].Value; //([^&;]*)string two = match.Groups[2].Value; //(?=(;|&|$))return checkEntity(one, two);}private string ConverMatchValidQuotes(Match match){string one = match.Groups[1].Value; //(>|^)string two = match.Groups[2].Value; //([^<]+?)string three = match.Groups[3].Value;//(<|$)return one + regexReplace(P_QUOTE, "\"", two) + three;}public bool isAlwaysMakeTags(){return alwaysMakeTags;}public bool isStripComments(){return stripComment;}class Item{public string name { get; set; }public List<string> parameter { get; set; }}}
在请求时对参数的内容进行过滤：
var nHtmlFilter = new NHtmlFilter(false);surveyPayload.PayloadContent = nHtmlFilter.filter(surveyPayload.PayloadContent);
再次请求时，已将危险代码转成HTML转义字符串的形式了
