WordPress 5.9 Cross Site Scripting

Document Title:
===============
WordPress <= 5.9 Cross-Site Scripting  Reflected (Authenticated)


Credits & Authors:
==================
Taurus Omar [[email protected]]


Disclosure Type:
================
Independent Security Research


Release Date:
=============
2022-31-01


Vulnerability Disclosure Timeline:
==================================
2022-05-02: Public Disclosure


Vulnerability  CVE
===================
Pending (CVE-xxxxx)


Vulnerability Class:
====================
Cross Site Scripting - Reflected


Product & Service Introduction:
===============================
WordPress (WP, WordPress.org) is a free and open-source content
management system (CMS) written in PHP[4] and paired with a MySQL or
MariaDB database. Features include a plugin architecture and a template
system, referred to within WordPress as Themes. WordPress was
originally
created as a blog-publishing system but has evolved to support other
web
content types including more traditional mailing lists and forums,
media
galleries, membership sites, learning management systems (LMS) and
online
stores. One of the most popular content management system solutions in
use,
WordPress is used by 42.8% of the top 10 million websites as of October
2021.


Vendor HomePage
===============================
https://wordpress.org/download/


Abstract Advisory Information:
==============================
An independent vulnerability  researcher discovered a reflected cross
site web vulnerability in wordpress framwork.


Affected Product(s):
====================
All wordpress version <= 5.9


Discovery Status:
=================
Published


Exploitation Technique:
=======================
Local


Severity Level:
===============
Medium


Proof of Concept (PoC):
=======================
Reflected XSS is done when a user with the AUTHOR or CONTRIBUTOR role
adds a javascript payload in the Post's Excerpt function, whenever a
user wants to use the Add Block function in their post or page, the XSS
will be executed.  Also the post and page editor allows executing the xss payload
directly just by copying and pasting the malicious javascript.

## POC1:The malicious Excerpt will be executed in the post and page
sections at the moment you want to use the add new block function and
typing some name in the search engine of the add block function
reflecting it in all the wordpress editor sections.

1.) Login whit user author or contributor
2.) Add new post
3.) Add Block Post Excerpt
4.) Add malicious code in the Extract function (<object data="javascript:alert(0)">)
5.) Replicated

## POC2 IN BLOCK FUCTION
1.) Login whit user author
2.) Add new post
3.) Publish Post
4.) Add malicious code in the Extract function (<object data="javascript:alert(0)">)
5.) In the post editor add a new block
6.) Search for something in the block search engine7.) Replicated

## POC3: XSS IN POST & PAGE EDITOR
1.) Login whit user author or contributor
2.) Add new post
3.) Copy & Page (<object data="javascript:alert(0)">) in editor4.)
4.) Replicated


## Firefox Payload:
<object data="javascript:alert('xss')">
<object data=/ onload=alert(1)>
<iframe src="javascript:alert(1)">

## Chrome Payload:
<form><button formaction=javascript:alert(1)>XSS
<iframe src="javascript:alert(1)">
<form action=javascript:alert(1)><input type=submit value=XSS>

## Poc Image:
https://i.imgur.com/WiaEUEE.png
https://i.imgur.com/voJptm0.png

## Poc Video
https://www.youtube.com/watch?v=UEgEMADeOC8


Solution - Fix & Patch:
=======================
The vulnerability can be resolved by a encode and secure parse / escape
of the inputs.  In a second step the output location were the execute occurs needs
to be sanitized.


## Impact
Cross-Site Scripting, XSS will be executed, since in all the sections
where the editor and search engine of the add block function can be
used as well as in the post and page section of the editor with the copy and
paste function.


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