CVE-2026-12900 is a stored cross-site scripting vulnerability (CWE-79) in the Spectra Legacy – Gutenberg Blocks WordPress plugin by brainstormforce. The issue exists in the uagb/image block due to inadequate input sanitization and output escaping, enabling authenticated attackers with Contributor-level privileges or higher to inject arbitrary web scripts. These scripts execute in the context of users viewing the compromised pages, potentially leading to information disclosure or session hijacking. The vulnerability affects all versions up to and including 2.19.28. No official patch or remediation guidance has been provided at the time of this report.

An attacker with Contributor-level or higher access can inject malicious scripts into pages via the vulnerable block. These scripts execute in the browsers of users who visit the infected pages, potentially leading to theft of sensitive information, session tokens, or other malicious actions within the context of the affected site. The vulnerability does not impact availability but compromises confidentiality and integrity to a limited extent. The CVSS score is 6.4 (medium severity) reflecting network attack vector, low attack complexity, and privileges required.

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 removing or disabling the vulnerable uagb/image block if possible. Monitor official channels from brainstormforce for updates or patches addressing this vulnerability.