Background to this: Chrome ignores all the standard ways of saying “don’t autofill this textbox”, because site owners were using them to defeat the “remember my password” feature, and Google decided that overriding that decision was a net positive for security. (Probably true!)
However, this means that anything that Chrome guesses is a login box gets the autofill treatment, and it’s an ongoing battle to dissuade it. I’m going to try using a larger spray bottle this time; let’s see what happens. This change should go live tomorrow.