This article is a part of our Vulnerability Database (back to index)
Cross-site Scripting occurrences in Yoast Seo
The yoast_seo (aka Yoast SEO) extension before 7.2.3 for TYPO3 allows XSS. (2021-08-13, CVE-2021-36788)
A Stored Cross-Site Scripting vulnerability was discovered in the Yoast SEO WordPress plugin before 3.4.1, which had built-in blacklist filters which were blacklisting Parenthesis as well as several functions such as alert but bypasses were found. (2021-04-05, CVE-2021-24153)
The Yoast SEO plugin before 11.6-RC5 for WordPress does not properly restrict unfiltered HTML in term descriptions. (2019-07-09, CVE-2019-13478)
Why Cross-site Scripting can be dangerous
Cross site scripting is an attack where a web page executes code that is injected by an adversary. It usually appears, when users input is presented. This attack can be used to impersonate a user, take over control of the session, or even steal API keys.
The attack can be executed e.g. when you application injects the request parameter directly into the HTML code of the page returned to the user:
https://server.com/confirmation?message=Transaction+Complete
what results in:
<span>Confirmation: Transaction Complete</span>
In that case the message can be modified to become a valid Javascript code, e.g.:
https://server.com/confirmation?message=<script>dangerous javascript code here</script>
and it will be executed locally by the user's browser with full access to the user's personal application/browser data:
<span>Confirmation: <script>dangerous javascript code here</script></span>