Network payload on submit includes attribution

What to fix

Ensure the form’s network submit payload still includes the attribution fields — not only the DOM.

Step-by-step fix

1. With DevTools Network open, submit the form and inspect the POST/FormData or JSON body for utm_* / gclid / fbclid.
2. If DOM hidden fields are filled but the POST drops them, allow-list those keys in the form plugin or custom handler (many “save only known meta” snippets strip unknown fields).
3. Disable security plugins that rewrite form POSTs for this path while testing.
4. Re-test until the payload shows the keys.

Confirm it is fixed

Re-scan and confirm B13 reports attribution in the submit network payload.