AMP for WP < 1.1.17 - Unauthenticated Stored Cross-Site Scripting via Comment Content Regex Transformation

Description

The AMP for WP – Accelerated Mobile Pages plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Comment Content via Regex Transformation in all versions up to, and including, 1.1.16 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The crafted payload uses only WordPress-permitted comment tags and attributes (an anchor with href and title), and the AMP sanitizer pipeline omits javascript: protocol blocking, meaning neither the comment save filter nor the AMP output stage removes the malicious URI introduced by the transformation.