AcyMailing <= 11.1.0 - Unauthenticated Stored Cross-Site Scripting via 'customField[]' Parameter

Summary

The AcyMailing plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the customField[] parameter of the public frontusers::subscribe endpoint in versions up to, and including, 11.1.0. This is due to insufficient input sanitization and output escaping in the acym_cleanVar() sanitizer, whose HTML-tag stripper only matches complete tags (requiring a closing '>'), together with SubscriberInsertion::replaceUserInformation() and the archive view template, which substitute the stored subscriber field value into the mail body and emit it without HTML encoding. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses the online-archive URL for the poisoned subscriber, including administrators who click the plugin-generated link in the Subscribers → History screen.

Timeline

1. Oct 13, 2026, 7:46 AM UTCCVE published
2. Oct 15, 2026, 10:48 AM UTCCISA SSVC assessment

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

3. Oct 15, 2026, 4:43 PM UTCRecord last updated

Affected versions

• acyba AcyMailing – An Ultimate Newsletter Plugin and Marketing Automation Solution for WordPress

  through 11.1.0

References 8