If the user added a security exception for an invalid TLS certificate, opened an ongoing TLS connection with a server that used that certificate, and then deleted the exception, Firefox would have kept the connection alive, making it seem like the certificate was still trusted. This vulnerability affects Firefox < 107.
38.8.0~repack1-0ubuntu138.8.0~repack1-0ubuntu338.8.0~repack1-0ubuntu452.3.1-0ubuntu352.3.1-7fakesync152.8.1-0ubuntu0.18.04.152.9.1-0ubuntu0.18.04.152.9.1-1build152.9.1-1ubuntu368.5.0-1~fakesync68.5.0-2~fakesync68.6.0-168.6.0-1ubuntu178.13.0-178.15.0-278.15.0-4ubuntu191.10.0-0ubuntu191.5.1-0ubuntu191.6.0-191.6.0-291.7.0-2Exploitability
AV:NAC:LPR:NUI:RScope
S:UImpact
C:NI:HA:NCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N