PureVPN Linux apps found to leak IPv6 traffic and mess with your firewall – here’s how to secure your data

PureVPN confirmed that it is working to patch these issues by mid-October, while ensuring that no other apps are vulnerable.
ZDNet

Yes, you need a firewall on Linux - here's why and which to use

Linux is highly secure, but you should still have a firewall. You should know if your ISP's hardware (gateway) uses a firewall. One of the easiest Linux firewalls is UFW and its GUI sidekick, GUFW.