You have zero control over what the shared account contains. The previous user might have sent abusive messages, participated in banned groups, or shared illegal content. By logging in, even temporarily, you could inadvertently become associated with that activity. Facebook’s systems log every action. An innocent browse could land you in serious trouble.
If you've lost your password or want to browse privately, try these official methods: facebook login password bugmenot
If you simply want to view public content without logging in, try these methods: You have zero control over what the shared account contains
Instead of stealing someone else’s login, create your own anonymous account. Facebook’s terms require your real name, but millions of users create pseudonymous accounts for privacy. Use a disposable email address, a VPN, and never provide your real phone number. Unlike a BugMeNot account, you control this account, and you can set your privacy settings to maximum. Facebook’s systems log every action