The Autoptimize plugin for WordPress suffers from a stored XSS vulnerability due to improper neutralization of input in the LCP Image to preload metabox feature. Specifically, the "create_img_preload_tag" function fails to adequately sanitize and escape user-supplied image attributes, enabling authenticated attackers with contributor or higher privileges to inject arbitrary JavaScript code. This code executes in the context of any user who accesses the compromised page, potentially leading to session hijacking or other client-side attacks. The vulnerability affects all versions up to 3.1.13 and has a CVSS 3.1 base score of 6.4 (AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N).

An attacker with contributor-level or higher access can inject persistent malicious scripts into pages via the vulnerable image preload feature. These scripts execute in the browsers of users who visit the infected pages, potentially leading to information disclosure or session compromise. The impact is limited to confidentiality and integrity loss without availability impact. There are no known exploits in the wild as of the publication date.

Patch status is not yet confirmed — no official patch or remediation guidance is provided in the available data. Users should monitor the vendor's advisory channels for updates. Until a fix is available, restrict contributor-level access to trusted users and consider disabling or limiting use of the LCP Image to preload metabox feature if possible.