Mozilla has provided an update to Firefox version 118.0.1 to close a vulnerability that is already being used to attack Chrome users. An update is also available for Firefox ESR 115.3.
It should also be noted here (you know, TL;DR) that it's also fixed in:
Firefox ESR 115.3.1
Firefox Focus for Android 118.1
Firefox for Android 118.1
Thunderbird 115.3.1
Anyone using Tor browser should know that they should check it's updating status before using it. Thankfully it checks itself but still, stay up to date before you browse.