The Filestack WP Upload WordPress plugin suffers from a reflected cross-site scripting vulnerability (CWE-79) due to improper neutralization of input during web page generation. Specifically, the 'fstab' and 'filestack_options' parameters are not properly sanitized or escaped, allowing unauthenticated attackers to inject arbitrary JavaScript code. This code executes in the context of the victim's browser if they are tricked into interacting with a maliciously crafted link. The vulnerability affects all versions up to 2.1.0. The CVSS 3.1 vector is AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N, reflecting network attack vector, low attack complexity, no privileges required, user interaction required, scope changed, and low confidentiality and integrity impacts with no availability impact.

Successful exploitation allows an attacker to execute arbitrary scripts in the context of the victim's browser, potentially leading to theft of sensitive information or session hijacking. The impact is limited to confidentiality and integrity with no direct availability impact. The vulnerability requires user interaction and does not require authentication.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, users should exercise caution with links involving the Filestack WP Upload plugin parameters and consider disabling or removing the plugin if feasible. Monitor vendor channels for updates and apply patches promptly once available.