Facebook has a rarely-mentioned feature under Password and Security > Password Checkup. It scans your saved passwords against known breach databases (including public indexes) and alerts you if you need to change them.
Let’s say you are a security researcher or you accidentally stumble upon a directory containing your exact Facebook password. Do not panic. Index Of Password Facebook
If you are genuinely interested in understanding how Facebook passwords might be at risk, join the Facebook Bug Bounty Program (facebook.com/whitehat). Ethical hackers and security researchers can legally test Facebook’s systems. If you find a vulnerability (like an exposed internal server index), Facebook pays you—often between $500 and $50,000+ per bug. Facebook has a rarely-mentioned feature under Password and
What you cannot do: search for third-party stolen credential indexes, download them, or attempt to use them. That is not research; it is computer crime. Do not panic