SecurityError? The operation is insecure? Wuh?
Making matters worse, my colleague seemed to have no problems using Firefox. But I was consistently reproducing the problem on two different work machines, and on my home machine.
Eventually tracked the root problem down: the issue is because of my default cookie settings:
Easy problem to solve once you know what’s going on, and I suspect that not many people configure their Firefox the way I do, so I don’t think it’s too big a deal. But I’m also pretty sure that there aren’t any web pages that describe this problem because I kinda searched.