CVE-2026-17586 describes a stored cross-site scripting vulnerability in the VK All in One Expansion Unit WordPress plugin (versions up to 9.118.0). The flaw is due to improper neutralization of input during web page generation, specifically in the handling of the 'vkExUnit_cta_img_position' post meta. The plugin applies a sanitize_text_field callback on save, which does not remove double-quote characters or on* event-handler attributes. Additionally, the output filter Vk_Call_To_Action::safe_kses_post() only rewrites disallowed iframe elements but returns other content verbatim, leaving injected scripts intact in the HTML output. This allows authenticated attackers with contributor or higher privileges to inject arbitrary web scripts that execute in the context of users viewing the affected pages.

An attacker with contributor-level or higher access can inject persistent malicious scripts into pages, which execute in the browsers of users who view those pages. This can lead to information disclosure or session hijacking. The CVSS 3.1 base score is 6.4 (medium severity), reflecting network attack vector, low attack complexity, privileges required, no user interaction, and impacts on confidentiality and integrity but not availability.

No official patch or fix is currently documented. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, restrict contributor-level access to trusted users only and consider disabling or limiting the use of the vulnerable post meta field. Monitor vendor communications for updates and apply official patches promptly once released.