Executive brief
JetFormBuilder is a popular WordPress form builder plugin used to create contact and submission forms. The plugin fails to properly sanitize user-submitted form data before including it in HTML email notifications sent to administrators. An attacker can inject arbitrary HTML and scripts into these emails, which may execute depending on the recipient's email client, compromising the confidentiality and integrity of administrator communications.
Technical details
The vulnerability is a stored HTML injection (CWE-79) in the email notification functionality. Unauthenticated users can submit form data containing HTML-entity-encoded payloads (e.g., "<img src=x onerror=alert()>") which bypass sanitization filters because decoding happens after filtering, not before. The injected HTML is then embedded in HTML-formatted notification emails sent via the "Send Email" post-action. An attacker needs only to identify a publicly accessible form with WYSIWYG or similar fields configured to send HTML emails. The payload is stored and rendered in emails to site administrators and other recipients; whether JavaScript executes depends on the mail client's HTML rendering behavior. The vulnerability is fixed in version 3.6.5.2.
Affected products
- Crocoblock JetFormBuilder before 3.6.5.2
Timeline
- 2026-09-03: disclosed
- 2026-09-05: advisory
- 2026-09-05: patched: Fix available in version 3.6.5.2