I have multiple pinned tabs in my Firefox windows.
I have Firefox reload my previous windows and tabs when it starts.
Firefox auto-loads the content of all pinned tabs, plus whichever non-pinned tab is focused, if it's one of those instead of a pinned tab.
It appears that some of my pinned tabs trigger prompting for the Master Password.
Each new popup for Master Password grabs input focus away from wherever it was, including any other Master Password popup.
As such I can be part way through (quickly as I can!) typing the password into one prompt when focus is yanked away into a new popup.
Suggestion: Implement some sort of locking mechanism on the Master Password popup such that there is only ever one present. Any subsequent new/additional need for the master password should instead find and re-focus/alert the extant popup.
Whilst there are other suggestions to make pinned tabs not auto-load I'm actually not 100% confident that pinned tabs are the only cause of this multiple master password popup behaviour, I'm mostly offering it as a possible extra reproduction step, i.e. any testing around the master password popup behaviour should take into account if pinned tabs auto-loading can cause additional such popups to be created.
