I heard that if you file share with someone on accident, they can gain access to your mac if they know the password to your mac. Could someone who I accidentally file shared with login to my mac if I did not have an admin password at the time?

I know it was stupid to not have a computer password at the time, but I now do. Could this be possible?

Welcome to Apple Support Communities
This would only happen if you choose the whole hard drive as a shared folder, and it's not. By default, OS X only sets up File Sharing in order to share files through the Public folder. You can see which folders are being shared in System Preferences > Sharing > File Sharing.
If the whole hard drive is selected as a shared folder, remove it because they can access to all your files without any password. Apart from that, there's no risk, as they can't see any other folder than the ones you chose in System Preferences > Sharing

Similar Messages

Maybe you are looking for