Our current design with the Sync Key does not mask that field. This decision was made mostly to help reduce errors entering a random 20 character key on mobile devices. However, users entering a custom Sync Key (ie secret phrase) are now suddenly looking at their secret phrase in plain view (as we don't mask it). This causes confusion and is generally not a great practice. Can we provide an option that users can select to reveal the Sync Key, but mask it by default? This would be similar to what OS X does for your WiFi key, for example (thanks to mconnor for that idea, I'd totally forgotten about that). We should also do this for Firefox Home and the Fennec UI.