Description

The a3 Lazy Load plugin for WordPress is vulnerable to Stored Cross-Site Scripting in all versions up to, and including, 2.7.6 This is due to a regex bug in the _filter_videos() method that breaks HTML attribute quoting when processing crafted <video> elements, combined with unescaped output in the admin/views/form-data.php template. An authenticated attacker with Contributor-level access can insert a crafted <video> tag whose src attribute contains an embedded class=" substring that tricks the plugin's class-replacement regex into consuming an attribute-value closing quote. This shifts the HTML5 parser's quote boundary, promoting attacker-controlled text from inside a quoted attribute value into standalone event-handler attributes (autofocus, onfocus). The injected script executes in the browser of any user (including administrators) who views the post.

Weaknesses 1

References 8

• plugins.trac.wordpress.org https://plugins.trac.wordpress.org/browser/a3-lazy-load/trunk/admin/views/form-data.php#L11
• plugins.trac.wordpress.org https://plugins.trac.wordpress.org/browser/a3-lazy-load/trunk/classes/class-a3-lazy-load.php#L124
• plugins.trac.wordpress.org https://plugins.trac.wordpress.org/browser/a3-lazy-load/trunk/classes/class-a3-lazy-load.php#L136
• plugins.trac.wordpress.org https://plugins.trac.wordpress.org/browser/a3-lazy-load/trunk/classes/class-a3-lazy-load.php#L623
• plugins.trac.wordpress.org https://plugins.trac.wordpress.org/browser/a3-lazy-load/trunk/classes/class-a3-lazy-load.php#L643
• plugins.trac.wordpress.org https://plugins.trac.wordpress.org/browser/a3-lazy-load/trunk/classes/class-a3-lazy-load.php#L666
• plugins.trac.wordpress.org https://plugins.trac.wordpress.org/changeset?old_path=%2Fa3-lazy-load/tags/2.7.6&new_path=%2Fa3-lazy-load/tags/2.7.7
• wordfence.com https://www.wordfence.com/threat-intel/vulnerabilities/id/5246efbb-93cc-4951-900e-d13d08840f03?source=cve

Remediation