How to change my facebook password back?

[Jasmine Greene]

So i accidentally changed my sisters facebook password instead of mine (don't ask how! Lol) Is there a way i can change it back to its original password so she doesn't know i changed hers?
I don't know her original password so i can't just change it - can i undo a password change?
Please ask if this is unclear! It is quite confusing...!

[Elaine]

Nope, there's no undo. Shouldn't be fraping your sister!

[Scruffy]

How did you manage this? It's not possible to change a password on any application without knowing the original.

[sagar.naik07]

yes there is one possibility to make it old password as it is. go to email id provider. login account as your new password and check there facebook mails. find first mail from facebook i.e welcome mail i hope in that mail u get it.

[Pwincess H]

put it your sisters old password, surely fb asked you for old password in other to change it so you do know. You must be the hacker!