I wish to request a change in product functionality to make it harder for phone scammers to steal money from people.
Common sense would have it that you should never login to online banking when somebody is remotely accessing your computer, but a lot of scams rely on people doing this (as seen on YouTube): you get a robocall, and if you choose to speak to a live agent, they request remote access to your computer. Then they tell you to login to online banking to get a "refund" but they alter the webpage to make it look like they "accidentally" refunded an excessively large amount of money to your bank account. Then they try to get you to pay the "excess" amount "back" to them.
This scam relies on the "feature" of some remote assistance software to blank the screen for local users while the scammer uses the developer tools to alter the content of online banking web pages to show fake transactions, etc. Ideally, Mozilla Firefox should be able to detect if somebody is using remote control software to view the user's screen.
If a remote user (such as somebody using AnyDesk, GotoAssist, TeamViewer, or LogMeInRescue) accesses the developer tools to alter the appearance of a web page, there should be a prominent blinking warning that the content may have been altered. Only a person locally accessing the computer should be able to suppress the warning, and the warning should not be able to be suppressed at all if the person is accessing an online banking site unless they're accessing it from an IP address registered to the bank.
Detection of online banking sites may be done by downloading a list of legitimate banking sites from financial regulation authorities, such as the FDIC. Not sure how one would programmatically detect whether the computer is being remote controlled, but if this is not technically feasible, then just put the prominent blinking warning anytime somebody uses the developer menu to alter the appearance of a web page. To suppress the warning, you can produce a separate "developer edition" of Firefox (not to be confused with beta or alpha testing builds - but rather, simply a version where the "developer tools" don't display a warning.) (Or, in the alternative, an actual web developer can edit the HTML or Javascript in an external text editor and load the page from a file instead of the live website.)