Develop Reference

Detect if string contains javascript tags using jQuery/JavaScript

I am trying to create a very simplistic XSS detection system for a system I am currently developing. The system as it stands, allows users to submit posts with javascript embedded within the message. Here is what I currently have:-
var checkFor = "<script>";
alert(checkFor.indexOf("<script>") !== -1);
This doesn't really work that well at all. I need to write code that incorporates an array which contains the terms I am searching for [e.g - "<script>","</script>","alert("]
Any suggestions as to how this could be achieved using JavaScript/jQuery.
Thanks for checking this out. Many thanks :)

Replacing characters is a very fragile way to avoid XSS. (There are dozens of ways to get < in without typing the character -- like < Instead, HTML-encode your data. I use these functions:
var encode = function (data) {
var result = data;
if (data) {
result = $("<div />").html(data).text();
}
};
var decode = function (data) {
var result = data;
if (data) {
result = $("<div />").text(data).html();
}
};

As Explosion Pills said, if you're looking for cross–site exploits, you're probably best to either find one that's already been written or someone who can write one for you.
Anyway, to answer the question, regular expressions are not appropriate for parsing markup. If you have an HTML parser (client side is easy, server a little more difficult) you could insert the text as the innerHTML of an new element, then see if there are any child elements:
function mightBeMarkup(s) {
var d = document.createElement('div');
d.innerHTML = s;
return !!(d.getElementsByTagName('*').length);
}
Of course there still might be markup in the text, just that it's invalid so doesn't create elements. But combined with some other text, it might be valid markup.

The most effective way to prevent xss attacks is by replacing all <, > and & characters with
<, >, and &.
There is a javascript library from OWASP. I haven't worked with it yet so can't tell you anything about the quality. Here is the link: https://www.owasp.org/index.php/ESAPI_JavaScript_Readme

Wrap every occurrence of the text "Rs." with <span class="someClass">

I have the currency "Rs." occurring on multiple places on my site. I want to wrap every occurrence of the text with <span class="WebRupee">. But if it is already wrapped with <span class="WebRupee"> it should be ignored.
I cannot use $('*:contains("Rs.")').wrap("<span class=\"WebRupee\"); because this wraps the html around the node that contains Rs. but not around the text alone. And for the same reason I cannot use .wrapInner();
Again any help will be greatly appreciated!
EDIT : the javascript provided on the webrupee site doesn't work on my site(no clue why). So that's out of the question as a solution. And hence I thought of writing a custom javascript. Just don't know how I could approach this.
EDIT(2): thinking out loud - hmm is there a way to add html at the indexOf("Rs.") ..or a simmilar approach

First, what you are trying to do is a dirty hack.
You should fix it in the source, whatever it is (for example PHP backend, Ruby backend, plain HTML, etc...).
See this example working at http://jsfiddle.net/8jXLw/
I did many assumptions and simplifications, your Regular Expressions should be more complete.
var spanit = function(item) {
var $item = jQuery(item);
var regexp = /\d+ Rs\./;
var text = $item.text();
if (!regexp.test(text)) {
return;
}
if ($item.has(".WebRupee").length) {
return;
}
var new_text = text.replace(" Rs."," <span class='WebRupee'>Rs.</span>");
$item.html(new_text);
};
jQuery(function() {
$("p.test").each(function() {
spanit(this);
});
});

Use http://cdn.webrupee.com/js file. it is working fine. i had used for one website.
If you want download and customize little..
thanks..

very inefficient solution
var replaced = $("body").html().replace('Rs.','<span class="WebRupee">Rs.</span>');
$('body').html(replaced);
var replaced = $("body").html().replace('<span class="WebRupee"><span class="WebRupee">Rs.</span></span>','<span class="WebRupee">Rs.</span>');
$('body').html(replaced);

Replace all strings "<" and ">" in a variable with "<" and ">"

I am currently trying to code an input form where you can type and format a text for later use as XML entries. In order to make the HTML code XML-readable, I have to replace the code brackets with the corresponding symbol codes, i.e. < with < and > with >.
The formatted text gets transferred as HTML code with the variable inputtext, so we have for example the text
The <b>Genji</b> and the <b>Heike</b> waged a long and bloody war.
which needs to get converted into
The <b>Genji</b> and the <b>Heike</b> waged a long and bloody war.
I tried it with the .replace() function:
inputxml = inputxml.replace("<", "<");
inputxml = inputxml.replace(">", ">");
But this would just replace the first occurrence of the brackets. I'm pretty sure I need some sort of loop for this; I also tried using the each() function from jQuery (a friend recommended I looked at the jQuery package), but I'm still new to coding in general and I have troubles getting this to work.
How would you code a loop which would replace the code brackets within a variable as described above?
Additional information
You are, of course, right in the assumption that this is part of something larger. I am a graduate student in Japanese studies and currently, I am trying to visualize information about Japenese history in a more accessible way. For this, I am using the Simile Timeline API developed by MIT grad students. You can see a working test of a timeline on my homepage.
The Simile Timeline uses an API based on AJAX and Javascript. If you don't want to install the AJAX engine on your own server, you can implement the timeline API from the MIT. The data for the timeline is usually provided either by one or several XML files or JSON files. In my case, I use XML files; you can have a look at the XML structure in this example.
Within the timeline, there are so-called "events" on which you can click in order to reveal additional information within an info bubble popup. The text within those info bubbles originates from the XML source file. Now, if you want to do some HTML formatting within the info bubbles, you cannot use code bracket because those will just be displayed as plain text. It works if you use the symbol codes instead of the plain brackets, however.
The content for the timeline will be written by people absolutely and totally not accustomed to codified markup, i.e. historians, art historians, sociologists, among them several persons of age 50 and older. I have tried to explain to them how they have to format the XML file if they want to create a timeline, but they occasionally slip up and get frustrated when the timeline doesn't load because they forgot to close a bracket or to include an apostrophe.
In order to make it easier, I have tried making an easy-to-use input form where you can enter all the information and format the text WYSIWYG style and then have it converted into XML code which you just have to copy and paste into the XML source file. Most of it works, though I am still struggling with the conversion of the text markup in the main text field.
The conversion of the code brackets into symbol code is the last thing I needed to get working in order to have a working input form.

look here:
http://www.bradino.com/javascript/string-replace/
just use this regex to replace all:
str = str.replace(/\</g,"<") //for <
str = str.replace(/\>/g,">") //for >

To store an arbitrary string in XML, use the native XML capabilities of the browser. It will be a hell of a lot simpler that way, plus you will never have to think about the edge cases again (for example attribute values that contain quotes or pointy brackets).
A tip to think of when working with XML: Do never ever ever build XML from strings by concatenation if there is any way to avoid it. You will get yourself into trouble that way. There are APIs to handle XML, use them.
Going from your code, I would suggest the following:
$(function() {
$("#addbutton").click(function() {
var eventXml = XmlCreate("<event/>");
var $event = $(eventXml);
$event.attr("title", $("#titlefield").val());
$event.attr("start", [$("#bmonth").val(), $("#bday").val(), $("#byear").val()].join(" "));
if (parseInt($("#eyear").val()) > 0) {
$event.attr("end", [$("#emonth").val(), $("#eday").val(), $("#eyear").val()].join(" "));
$event.attr("isDuration", "true");
} else {
$event.attr("isDuration", "false");
}
$event.text( tinyMCE.activeEditor.getContent() );
$("#outputtext").val( XmlSerialize(eventXml) );
});
});
// helper function to create an XML DOM Document
function XmlCreate(xmlString) {
var x;
if (typeof DOMParser === "function") {
var p = new DOMParser();
x = p.parseFromString(xmlString,"text/xml");
} else {
x = new ActiveXObject("Microsoft.XMLDOM");
x.async = false;
x.loadXML(xmlString);
}
return x.documentElement;
}
// helper function to turn an XML DOM Document into a string
function XmlSerialize(xml) {
var s;
if (typeof XMLSerializer === "function") {
var x = new XMLSerializer();
s = x.serializeToString(xml);
} else {
s = xml.xml;
}
return s
}

https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/String/replace
You might use a regular expression with the "g" (global match) flag.
var entities = {'<': '<', '>': '>'};
'<inputtext><anotherinputext>'.replace(
/[<>]/g, function (s) {
return entities[s];
}
);

You could also surround your XML entries with the following:
<![CDATA[...]]>
See example:
<xml>
<tag><![CDATA[The <b>Genji</b> and the <b>Heike</b> waged a long and bloody war.]]></tag>
</xml>
Wikipedia Article:
http://en.wikipedia.org/wiki/CDATA

What you really need, as mentioned in comments, is to XML-encode the string. If you absolutely want to do this is Javascript, have a look at the PHP.js function htmlentities.

I created a simple JS function to replace Greater Than and Less Than characters
Here is an example dirty string: < noreply#email.com >
Here is an example cleaned string: [ noreply#email.com ]
function RemoveGLthanChar(notes) {
var regex = /<[^>](.*?)>/g;
var strBlocks = notes.match(regex);
strBlocks.forEach(function (dirtyBlock) {
let cleanBlock = dirtyBlock.replace("<", "[").replace(">", "]");
notes = notes.replace(dirtyBlock, cleanBlock);
});
return notes;
}
Call it using
$('#form1').submit(function (e) {
e.preventDefault();
var dirtyBlock = $("#comments").val();
var cleanedBlock = RemoveGLthanChar(dirtyBlock);
$("#comments").val(cleanedBlock);
this.submit();
});

Making links clickable in Javascript?

Is there an simple way of turning a string from
Then go to http:/example.com/ and foo the bar!
into
Then go to example.com and foo the bar!
in Javascript within an existing HTML page?

Yes. The simplest way is to use a regular expressions to substitute things that look like a link for their linked equivalents. Something like:
node.innerHTML = node.innerHTML.replace(/(http:\/\/[^\s]+)/g, "<a href='$1'>$1</a>")
(my RegEx is a little rusty, so you may need to play with the syntax). This is just a simple case. You need to be wary of script injection here (for example if I have http://"><script>doevil()</script>). One way to work around this is by using a link building function:
node.innerHTML = node.innerHTML.replace(/ ... /g, buildLink($1));
Where buildLink() can check to make sure the URL doesn't contain anything malicious.
However, the RegEx-innerHTML method will not perform very well on large bodies of text though, since it tears down and rebuilds the entire HTML content of the node. You can achieve this with DOM methods as well:
Find reference to the text node
In the content, find start and end indexes of a URL
Use splitText() method to split the node into 3: before, link, after
Create an <a> node with the href that's the same as the link
Use insertBefore() to insert this <a> node before the link
Use appendChild() to move the link into the <a> node

First, "within an HTML page" is difficult because a "page" is actually a DOM tree (which is partially composed of text nodes and mostly composed of HTML elements).
The easiest way to approach this problem would be to target content-rich text nodes. For each text node, apply something like this:
// we'll assume this is the string of a content-rich text node
var textNode = document.getElementById('contentNode');
textNode.innerHTML = textNode.innerHTML.replace(/(\s)(http:\/\/[^\s]+)(\s)/g, '$1$2$3');
BTW: there are security implications here. If you generate links from unsterilized text, there is the possibility of XSS.

I use a function utilizing regex (regular expressions) to make it easier to do this. Some docs and some regex cheatsheets are linked below.
function linkfun(text, https) {
if(https == "both") { // both
var urlRegex = /(https?:\/\/[^\s]+)/g; // regex for both http:// and https://
return text.replace(urlRegex, function(url) {
return '' + url + ''; // return the replaced text
})
}
if(https == true) {
var urlRegex = /(https:\/\/[^\s]+)/g; // regex for only https:// (notice the missing "?")
return text.replace(urlRegex, function(url) {
return '' + url + ''; // return the replaced text
})
} else {
var urlRegex = /(http:\/\/[^\s]+)/g; // regex for only http:// (notice the missing "?")
return text.replace(urlRegex, function(url) {
return '' + url + ''; // return the replaced text
})
}
// or alternatively
// return text.replace(urlRegex, '$1')
}
<p id="text">Hi!! https://example.org is my favourite website, but http://example.net is also good. http://stackoverflow.com and https://stackexchange.com are cool. https://www.firefox.com is a web browser.<br><br>If you want to use this function multiple times on the same text, use <code>linkfun(...innerText, ...)</code> instead of <code>linkfun(...innerHTML, ...)</code></p>
<button onclick="document.getElementById('text').innerHTML = linkfun(document.getElementById('text').innerHTML, true);">Change just HTTPS</button>
<button onclick="document.getElementById('text').innerHTML = linkfun(document.getElementById('text').innerHTML, false);">Change just HTTP</button>
<button onclick="document.getElementById('text').innerHTML = linkfun(document.getElementById('text').innerHTML, 'both');">Change both</button>
You can learn more about:
- regex at mdn devdocs caniuse cheatsheet (rexegg) cheatsheet (mdn)
- string:replace at mdn devdocs caniuse

Link terms on page to Wikipedia articles in pure JavaScript

While browsing I came across this blog post about using the Wikipedia API from JavaScript, to link a single search term to it's definition. At the end of the blog post the author mentions possible extensions including:
A plugin which auto links terms to Wikipedia articles.
This fits the bill perfectly for a project requirement I'm working on, but sadly I lack the programming skills to extend the original source code. What I'd like is to have a pure JavaScript snippet I can add to a webpage, that links all the terms on that webpage that have an article on an internal wiki to that wiki.
I know this might be asking for much, but the code looks like it's nearly there, and I'd be willing to add a bounty if anyone will do the remaining work for that virtual credit.. ;) I also suspect this might be of value to a few others, as I've seen similar requests but no working implementation (that's a mere JavaScript (and therefore portable) library/snippet include).
Here's a sample of the original source code, I hope anyone is able to add to this or point me to what I'd need to add if I were to implement this myself (in which case I'll share the code if I manage to put something together).
<script type="text/javascript"><!--
var spellcheck = function (data) {
var found = false; var url=''; var text = data [0];
if (text != document.getElementById ('spellcheckinput').value)
return;
for (i=0; i<data [1].length; i++) {
if (text.toLowerCase () == data [1] [i].toLowerCase ()) {
found = true;
url ='http://en.wikipedia.org/wiki/' + text;
document.getElementById ('spellcheckresult').innerHTML = '<b style="color:green">Correct</b> - <a target="_top" href="' + url + '">link</a>';
}
}
if (! found)
document.getElementById ('spellcheckresult').innerHTML = '<b style="color:red">Incorrect</b>';
};
var getjs = function (value) {
if (! value)
return;
url = 'http://en.wikipedia.org/w/api.php?action=opensearch&search='+value+'&format=json&callback=spellcheck';
document.getElementById ('spellcheckresult').innerHTML = 'Checking ...';
var elem = document.createElement ('script');
elem.setAttribute ('src', url);
elem.setAttribute ('type','text/javascript');
document.getElementsByTagName ('head') [0].appendChild (elem);
};--></script>
<form action="#" method="get" onsubmit="return false">
<p>Enter a word - <input id="spellcheckinput" onkeyup="getjs (this.value);" type="text"> <span id="spellcheckresult"></span></p></form>
Update
As pointed out in the comments, both the time it would take to link all words and how to handle multiple word spanning article names were concerns of mine as well..
I'd think starting with single word articles would already cover a large percentage of the use cases, with maybe some performance benefits gained when skipping the 500 most common words in the English language, but still I'm uncertain how feasible this approach will be..
On the upside however this would all be client side, and some delay in linking terms is fully acceptable.
Alternatively searching for terms the mouse is hovering over / selected might be acceptable as well, but I'm unsure if this would decrease or increase complexity..
Update 2
'Pointy' explained below that this functionality could be achieved by altering some fairly standard highlighting scripts, after having obtained a list of article topics from api.php?action=query&list=allpages.
To reinterate: we're using an internal wiki, so the list of articles is likely limited, non ambiguous and domain specific enough to overcome some of the expected problems in matching words.
Since we've had some good suggestions so far, and a few workable ideas, I'm starting a bounty to see if I can get a few answers on this..

Perhaps something like this might help:
Assuming very simple HTML/Text like so:
<div id="theText">Testing the auto link system here...</div>
And two very small scripts.
dictionary.js sets up your list of your terms. My thought was that this could be generated in php by querying the articles database if you wanted. It also can be loaded cross domain (as it sets window.termsRE). If you don't need to generate the list from the database, you could also manually put it with termlinker.js.
This code that generates the RegExp assumes that your terms array contains properly formatted strings to match using Regular Expressions, so be sure to use \\ to escape []\.?*+|(){}^&
// dictionary.js - define some terms
var terms = ['testing', 'auto link'];
window.termsRE = new RegExp("\\b("+terms.join("|")+")\\b",'gi');
termlinker.js is just a simple regexp search replace on the defined terms. It could be an inline <script> too. requires that the dictionary.js has been loaded before you run it.
// termlinker.js - add some tags
var element = document.getElementById("theText");
element.innerHTML = element.innerHTML.replace(termsRE, function(term) {
return "<a href='http://en.wikipedia.org/wiki/"+escape(term)+"'>"+term+"</a>";
});
This simply searches for any words in the terms array and replaces them with a link to the term. Of course, it will also match properties and values inside HTML tags, which could break your markup a little.
All thrown together you get this (jsbin preview)
Using the API
Based off of the "minimum case" from before, here is the code sample for using the API to receive the list of words directly and the jsbin preview
// Utility Function
RegExp.escape = function(text) {
if (!arguments.callee.sRE) {
var specials = [
'/', '.', '*', '+', '?', '|',
'(', ')', '[', ']', '{', '}', '\\'
];
arguments.callee.sRE = new RegExp(
'(\\' + specials.join('|\\') + ')', 'g'
);
}
return text.replace(arguments.callee.sRE, '\\$1');
};
// JSONP Callback for receiving the API
function receiveAPI(data) {
var terms = [];
if (!data || !data['query'] || !data['query']['allpages']) return false;
var pages = data.query.allpages
for (var x in pages) {
terms.push(RegExp.escape(pages[x].title));
}
window.termsRE = new RegExp("\\b("+terms.reverse().join("|")+")\\b",'gi');
linkterms();
}
function linkterms() {
var element = document.getElementById("theText");
element.innerHTML = element.innerHTML.replace(termsRE, function(term) {
return "<a href='http://en.wikipedia.org/wiki/"+escape(term)+"'>"+term+"</a>";
});
}
// the apfrom=testing can be removed, it is only there so that
// we can get some useful terms near "testing" to work with.
// we are limited to 500 terms for the purpose of this demo:
url = 'http://en.wikipedia.org/w/api.php?action=query&list=allpages&aplimit=500&format=json&callback=receiveAPI' + '&apfrom=testing';
var elem = document.createElement('script');
elem.setAttribute('src', url);
elem.setAttribute('type','text/javascript');
document.getElementsByTagName('head')[0].appendChild (elem);