The default configuration of udev on Linux does not warn the user before enabling additional Human Interface Device (HID) functionality over USB, which allows user-assisted attackers to execute arbitrary programs via crafted USB data, as demonstrated by keyboard and mouse data sent by malware on a smartphone that the user connected to the computer.
RedHat claims it has no security impact: https://bugzilla.redhat.com/show_bug.cgi?id=672513#c6 Should we close this bug?
I thought it was bullshit from the start. ;)