We had something like this but for French. The website was used for real tests and assignments but the answers would be loaded somewhere even if the test/assignment would not show you if you got it wrong.
So we made a Javascript one-liner that would retrieve and fill in the answers.
The first edition also submitted them but the teacher could see how fast you completed a test so we removed that as students who normally could not pass the test suddenly had 100% and in 5 seconds of time.
In the end, manually removing, answering some answers wrong and waiting to submit made that class a breeze.
Too bad my French is now very bad but that wasn't something youth-me thought of at the time.