hello dhrider, yes unfortunately this means that the other person got access to all your passwords. though it is possible to clear the data on the sync servers, this won't help if the other account has already synced and downloaded the data to the other device, so you should consider all your passwords as compromised.

you should perform those steps as quickly as possible:

1. go to firefox > options > sync > manage account... and change the password for the sync account.
2. afterwards reset the recovery key in the same menu
3. then go through your saved password data (in the password manager), and visit the sites in question where you'll have to change the passwords one-by-one. this might be the most time consuming, but it is essential to protect your data as far as possible (start with important sites like financial institutions, your email account, etc.)...

in addition, please update firefox to the latest version - you are using an outdated version affected by numerous known security vulnerabilities which will put the integrity of your system and your personal data further at risk!

You should first change the password for that Sync account and generate a new Sync key to remove all data stored on this Sync account.

You can delete the account here:

• https://services.mozilla.com/ Firefox Sync » Home
• https://account.services.mozilla.com/

You can find the sync account password and the sync (recovery) key in the password manager on computers where a sync account with a specific e-mail address has been set up.

• Firefox/Tools > Security: Passwords: "Saved Passwords" > "Show Passwords"

Look for:

• chrome://weave (Mozilla Services Password)
• chrome://weave (Mozilla Services Encryption Passphrase)

If you know who did it, call the police / FBI.