False positive: Managed Php Detection blocks POST /kiosk with 403

Hi, my production form submission is being blocked by Vercel. POST /kiosk returns 403 Forbidden with X-Vercel-Mitigated: deny. Firewall Traffic shows managed_php_detection.

Time: November 2, 2026, 07:37:37 GMT X-Vercel-Id: sin1::2fvs7-1793605051899-9267ec82b318 Project URL: https://projectmagangpelindo-bukutamu.vercel.app

projectmagangpelindo-bukutamu.vercel.app

Kiosk: Buku Tamu Pelindo

Could someone help confirm whether this is a false positive and suggest the right next step? I attached screenshots of the response headers and Firewall Traffic.