As this IT-problem needs the actual programmer, where is the one/the group ?

'Sync is helping criminals to have access to all connections.

Firefox's built-in Sync feature? How is it doing that?

Here's how to turn Sync on/off for different categories of data, such as saved logins: How do I choose what information to sync on Firefox?

Does that resolve your concern? If not, please explain the problem in more detail.

You only need to disconnect Sync to prevent this.

• https://support.mozilla.org/en-US/kb/disable-firefox-sync
• https://support.mozilla.org/en-US/kb/ive-lost-my-firefox-sync-account-information

Sync isn't meant to be used as a backup and, with only one device connected, it's usefulness is limited.