CVE-2026-96558: Quiz and Survey Master (QSM) <= 11.2.6 - Unauthenticated Stored DOM-Based Cross-Site Scripting via 'qsm_hidden_questions' Parameter
The Quiz and Survey Master (QSM) – Quiz Maker & Survey Maker plugin for WordPress is vulnerable to Stored DOM-Based Cross-Site Scripting via the 'qsmhiddenquestions' parameter in all versions up to, and including, 11.2.6 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This requires the attacker to force the mlwresults INSERT to fail by submitting an over-length or duplicate qsmuniquekey value, which triggers the audit trail code branch that writes the unescaped payload to wpmlwqmaudittrail.formdata.
Affected Software
Event History
Frequently Asked Questions
What conditions must an attacker meet to trigger the vulnerable code path?
An attacker does not need authentication, but must submit a malicious qsm_hidden_questions value while causing the mlw_results INSERT operation to fail. The failure can be induced with an over-length or duplicate qsm_unique_key value, which causes the audit-trail branch to store the unescaped payload in wp_mlw_qm_audit_trail.form_data.
Who is exposed to the injected script?
The injected script executes when a user accesses the page containing the injected payload. Because the vulnerability is stored XSS, the attacker can plant the payload before a victim visits the affected page.
How can I determine whether an exploitation attempt may have occurred?
Review wp_mlw_qm_audit_trail.form_data for unexpected script-like or HTML content associated with qsm_hidden_questions submissions. Also investigate submissions using unusually long or duplicate qsm_unique_key values, since these are used to force the database INSERT failure required for this issue.