CVE-2026-15052 is a stored cross-site scripting vulnerability (CWE-79) in the umarbajwa MailChimp Subscribe Form, Optin Builder, PopUp Builder, Form Builder WordPress plugin. Versions up to and including 4.3.3 are affected due to improper neutralization of input during web page generation, specifically insufficient sanitization and escaping of form field values. This flaw enables unauthenticated attackers to inject malicious scripts that execute in the context of users visiting the compromised pages, potentially leading to information disclosure or session hijacking. The vulnerability has a CVSS 3.1 base score of 7.2 (AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N), indicating network exploitable with low attack complexity and no privileges or user interaction required, impacting confidentiality and integrity with scope change.

An unauthenticated attacker can exploit this vulnerability to inject and store malicious scripts within form field values. These scripts execute in the browsers of users who visit the affected pages, potentially allowing the attacker to steal sensitive information, hijack user sessions, or perform actions on behalf of the user. The vulnerability affects confidentiality and integrity but does not impact availability.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch information is provided at this time. Until a patch is available, users should consider disabling or restricting the vulnerable plugin to mitigate risk. Monitor vendor communications for updates on remediation.