The Divi theme for WordPress is vulnerable to Stored Cross-Site Scripting via the `redirect_url` parameter of the `et_pb_contact_form` shortcode in all versions up to, and including, 4.27.6. This is due to the `redirect_url` attribute being sanitized with `esc_attr()` instead of `esc_url()` before being rendered into the `data-redirect_url` HTML data attribute. Additionally, `redirect_url` is absent from the hardcoded `$url_options` array in `class-et-builder-element.php`, so it does not receive `esc_url_raw()` sanitization during shortcode parsing.
After a successful form submission, client-side JavaScript reads this data attribute and passes it directly to `window.location.href`, executing arbitrary JavaScript from a `javascript:` URI. This makes it possible for authenticated attackers, with Contributor-level access and above, to inject arbitrary web scripts in pages that execute whenever a user submits the contact form.
Attack Parameters
Impact Assessment
CVSS Vector v3.1