The Ultimate Member plugin for WordPress suffers from a stored XSS vulnerability due to improper neutralization of input in the Skype and Spotify URL parameters. This allows authenticated users with low privileges (subscriber-level and above) to inject arbitrary scripts that execute in the context of other users viewing the injected pages. The vulnerability affects all versions up to and including 2.8.4. The CVSS 3.1 base score is 5.4, reflecting network attack vector, low attack complexity, low privileges required, no user interaction, and impacts on confidentiality and integrity but not availability.

An attacker with subscriber-level access can inject persistent malicious scripts into pages via the Skype and Spotify URL parameters. These scripts execute when other users access the injected pages, potentially leading to session hijacking, defacement, or other client-side attacks. The impact is limited to confidentiality and integrity with no direct availability impact. There are no reports of active exploitation in the wild.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, restrict subscriber-level user permissions where possible and monitor for suspicious activity related to profile URL parameters. Avoid granting unnecessary privileges to untrusted users. Consider implementing web application firewall (WAF) rules to detect and block suspicious input in Skype and Spotify URL parameters.