The Ultimate Blocks – 25+ Gutenberg Blocks for Block Editor plugin for WordPress suffers from a stored cross-site scripting vulnerability (CWE-79) due to improper neutralization of input during web page generation. Authenticated attackers with Contributor-level privileges or higher can inject arbitrary web scripts via multiple widgets because the plugin does not sufficiently sanitize or escape user input. This leads to script execution in the context of users visiting the compromised pages. The vulnerability affects all versions up to and including 3.3.3. The CVSS 3.1 base score is 6.4, reflecting network attack vector, low attack complexity, privileges required, no user interaction, and partial impact on confidentiality and integrity.

An attacker with Contributor-level access or higher can exploit this vulnerability to inject persistent malicious scripts into pages generated by the plugin. These scripts execute in the browsers of users who view the infected pages, potentially leading to unauthorized actions such as session hijacking or data theft limited to the scope of the affected site. The vulnerability does not impact availability and requires authenticated access, limiting its severity to medium.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, restrict Contributor-level access to trusted users only and consider disabling or removing the affected widgets if possible. Monitor official Ultimate Blocks plugin channels for updates and apply patches promptly once available.