The WP-Members Membership Plugin for WordPress suffers from a stored cross-site scripting vulnerability (CWE-79) due to improper neutralization of input during web page generation. Specifically, the wpmem_user_memberships shortcode does not adequately sanitize or escape user-supplied attributes, enabling authenticated attackers with contributor-level privileges or above to inject malicious scripts. These scripts execute in the context of any user visiting the injected page, potentially leading to session hijacking or other script-based attacks. The vulnerability affects all plugin versions up to 3.5.2. The CVSS 3.1 base score is 6.4 (AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N), reflecting network attack vector, low attack complexity, and partial impact on confidentiality and integrity with no impact on availability. No patch or official fix has been documented yet.

An authenticated attacker with contributor-level access or higher can inject persistent malicious scripts into pages via the vulnerable shortcode. These scripts execute in the browsers of users who visit the affected pages, potentially allowing theft of user credentials, session tokens, or other sensitive information, as well as manipulation of page content. The vulnerability does not impact availability. The scope is changed (S:C), meaning the attack can affect resources beyond the attacker's privileges. Currently, no known exploits have been reported in the wild.

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 limiting use of the wpmem_user_memberships shortcode. Monitor official channels for updates and apply patches promptly once available.