The Post Category Gallery plugin for WordPress suffers from a stored XSS vulnerability due to improper neutralization of input in the 'postcategorygallery' shortcode. Specifically, attributes like total_width, color_scheme, and caption_font_size are not properly sanitized or escaped in the sc_horcatbar() function, leading to direct injection of arbitrary scripts into HTML attribute values. This enables authenticated attackers with contributor-level permissions or higher to embed malicious JavaScript that executes in the context of any user viewing the compromised page.

An attacker with contributor-level access or above can exploit this vulnerability to inject persistent malicious scripts into pages using the vulnerable shortcode. This can lead to the execution of arbitrary JavaScript in the browsers of users who visit the infected pages, potentially resulting in session hijacking, defacement, or other client-side attacks. The vulnerability does not affect availability but impacts confidentiality and integrity to a limited extent as indicated by the CVSS vector.

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 Post Category Gallery plugin if possible to prevent exploitation.