a3 Lazy Load <= 2.7.6 - Authenticated (Contributor+) Stored Cross-Site Scripting via Video Element

Summary

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.

Timeline

1. May 28, 2026, 6:45 AM UTCCVE published
2. May 28, 2026, 10:27 AM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. May 28, 2026, 10:34 AM UTCRecord last updated

Affected versions

• a3rev a3 Lazy Load

  through 2.7.6

References 8