Basically, what they wanted to do was to build a background process that detects when you're away from the PC and then pops up the message, so it's the first thing you see what you get back.
Unfortunately (or maybe not) the detection logic had a bug, which caused the message to pop up right away sometimes, spoiling the whole thing.
This unnecessary bullshit is how you introduce security bugs into software. Mozilla can preach all they want about security and privacy but this shows that it's all rotten to the core.