Websites and apps that promise free access to Instagram accounts are often designed for malicious purposes:

There is no "master key." There is no hidden database. Anyone selling "free Instagram passwords" is lying to you.

: Services offering "free followers" often require you to log in with your actual credentials, which are then used to hijack your account. Malwarebytes Legitimate Ways to Manage Your Account

You find a massive text file claiming to contain "10,000 Instagram IDs and passwords." You download it. You open it. You see lines like: john_doe: pizza123 jane_smith: ilovecats