CVE-2026-96558: CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in expresstech Quiz and Survey Master (QSM) – Quiz Maker & Survey Maker

CVE-2026-96558 describes a stored DOM-based cross-site scripting vulnerability in the Quiz and Survey Master (QSM) WordPress plugin, versions up to 11.2.6. The flaw is due to improper neutralization of input in the 'qsm_hidden_questions' parameter, allowing unauthenticated attackers to inject arbitrary scripts. Exploitation requires causing an mlw_results INSERT failure by submitting an over-length or duplicate qsm_unique_key, which leads to unescaped payloads being written to the wp_mlw_qm_audit_trail.form_data database field. This results in script execution in users' browsers when accessing the injected page.

Successful exploitation allows unauthenticated attackers to execute arbitrary JavaScript in the context of affected users, potentially leading to information disclosure and limited integrity impact. The CVSS 3.1 base score is 7.2 (high), reflecting network attack vector, low attack complexity, no privileges required, no user interaction, and impact on confidentiality and integrity but not availability.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, users should consider disabling or restricting access to vulnerable parameters and monitor for suspicious activity related to the 'qsm_hidden_questions' parameter. Avoid using affected versions in production environments if possible.