https://www.reddit.com/r/sysadmin/comments/1fq5ojq/99_cve_announced_is_a_rce_in_cups/
This bug is a "remote code execution" bug.
Basically, any computer with the CUPS service running, that's not behind a firewall... allows the attacker to add a printer, and run scripts as root.
The mitigation for now, is not to print anything, as the hack doesn't allow the attacker to start new printing jobs.
Something to consider... here in the USA i did
apt remove cups
apt remove cups-browsed
apt-mark hold cups-browsed
apt-mark hold cups
Or go offline to print. You can't hack without access. Shutting down wifi or pulling your wired lan cord would prevent hacking while you print.
Dump Firefox and UFW, and install Librewolf and Portmaster should fix the mess..