Executive brief
Drupal core, a widely-used open-source content management platform, contains a cross-site scripting (XSS) vulnerability in how it sanitizes HTMX JavaScript library attributes. An attacker with the ability to insert HTML into site content can execute malicious JavaScript in the browsers of site visitors, potentially stealing session tokens, modifying page content, or redirecting users to malicious sites.
Technical details
The vulnerability is an improper input neutralization (CWE-79) affecting Drupal core's XSS filter, which fails to sufficiently sanitize certain HTMX attributes introduced in Drupal core 11.2 and later. The attack vector is network-based and requires the attacker to have the ability to insert HTML with specific attributes into site content (e.g., through a vulnerable contributed module or privileged user account). Successful exploitation allows arbitrary JavaScript execution in visitor browsers. The vulnerability is mitigated by access controls—an attacker must first gain content insertion capabilities. Patches are available: Drupal 11.4.4, 11.3.14, and 10.6.x include hardening fixes; Drupal 11.2.x and below are end-of-life and receive no patches.
Affected products
- Drupal Drupal core 11.3.0 to 11.3.14, 11.4.0 to 11.4.4, 11.2.x and earlier
Timeline
- 2026-07-15: disclosed: Drupal Security Advisory SA-CORE-2026-011
- 2026-08-25: other: CVE-2026-15917 published to NVD