This is the best defense against credential stuffing, as a password alone will not grant access.

Utilize reputable services to check if your email has been part of a known breach.

Files downloaded from untrusted, illicit sources, especially those labeled as combolists, are frequently used to distribute malware.

Possessing or using stolen user credentials is illegal in many jurisdictions.

Cybercriminals use these lists for "credential stuffing" or "brute-force" attacks, testing the pairs on various websites (banking, social media, e-commerce) to gain unauthorized access.

To give you the most relevant information, are you looking into this for: (checking if your credentials are safe)? Cybersecurity research or testing? Protecting a business from credential stuffing? Combolists and ULP Files on the Dark Web - Group-IB

Ensure your passwords are not reused across different platforms.