Messenger can warn you about sketchy links without knowing what you clicked

Meta's Advanced Browsing Protection (ABP) for Messenger is an optional Safe Browsing feature that leverages a continually updated server-side watchlist and privacy-preserving cryptographic techniques to warn users about potentially malicious websites without exposing plaintext links to Meta. When a user taps a link, the client converts the URL into a bucket identifier, generates blinded cryptographic queries for link components, and sends them to the server; the server returns encrypted bucket data which the device decrypts and compares locally, displaying a warning if the link matches the blocklist. The document also provides step-by-step instructions for enabling or disabling ABP in the Messenger app.