Wp-Pretty Photo DOM Based XSS Vulnerability

Details
=======
Product: PrettyPhoto Plugin
Security-Risk: Moderate
Remote-Exploit: yes
Company: RHAINFOSEC
Website: http://services.rafayhackingarticles.net
Vendor-URL: https://github.com/scaron/prettyphoto
Vendor-Status: informed
Advisory-Status: published

Credits
=======
Discovered by: Rafay Baloch
http://services.rafayhackingarticles.net

Description
========
The worpdress pretty photo plugin appears to be vulnerable to a DOM based
xss, unlike other XSS, dom based xss occurs on the client side, thus
leaving all the server side defenses worthlesss. The issue occurs inside
the client side javascripts
where the source (User supplied input) is passed through a vulnerable sink
(Anything that creates/writes) without sanitsing/escaping the user supplied
input

More Details
=========


Line 623: hashIndex = getHashtag();

Inside the line 623, we see a variable hashIndex which calls th e
getHashtag() function, which is responsible for returning the user
supplied values after the hash.


Let's take a look at teh getHashtag() function:

getHashtag()
{
url=location.href;hashtag=(url.indexOf('#!')!=-1)?decodeURI
(url.substring(url.indexOf('#!')+2,url.length)):false;return
hashtag;};

The function getHashtag() is used for returning the user supplied input,
the function also checks if the user input contains the hash bang and then
returns the value.

setTimeout(function()
{
$("a[rel^='" + hashRel + "']:eq(" + hashIndex + ")").trigger('click'); },
50);

Finally we have the above line which is responsible for the cause of the
dom based xss, the $("a[rel^='" + hashRel + "']:eq(" + hashIndex + ")
writes the user supplied input to the dom without sanitising the input.

POC
===

http://target.com/#!%22%3E%3Cimg%20src=1%20onerror=prompt%280%29;%3E//

The issue was fixed by sanitising the "hashrel" input before returning it
to the user.

hashIndex = parseInt(hashIndex);
hashRel = hashRel.replace(/([ #;&,.+*~\':"!^$[\]()=>|\/])/g,'\\$1');


References
==========

http://www.rafayhackingarticles.net/2013/05/kali-linux-dom-based-xss-writeup.html