The Custom Field Suite plugin for WordPress suffers from a stored cross-site scripting vulnerability due to improper neutralization of input during web page generation. Specifically, the 'cfs[post_title]' parameter is not properly sanitized or escaped, allowing authenticated users with contributor or higher privileges to inject arbitrary JavaScript code. This code executes in the context of users who view the injected pages, potentially leading to session hijacking or other script-based attacks. The vulnerability affects versions up to and including 2.6.7. The CVSS 3.1 base score is 6.4, reflecting network attack vector, low attack complexity, required privileges at the contributor level, no user interaction, and impacts on confidentiality and integrity with no availability impact.

Successful exploitation allows authenticated contributors or higher to inject persistent malicious scripts into pages, which execute in the browsers of users who access those pages. This can lead to unauthorized actions performed on behalf of users, data theft, or session hijacking. The impact is limited to confidentiality and integrity with no direct availability impact. There are no known active exploits reported.

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. Consider applying web application firewall (WAF) rules to detect and block suspicious input patterns targeting the 'cfs[post_title]' parameter. Monitor plugin updates from the vendor and apply patches promptly once available.