That's a Firefox feature, please disable it in settings (maybe you accidentally enabled it?) Regardless, the website should probably capture the keys instead o

That's a Firefox feature, please disable it in settings (maybe you accidentally enabled it?) Regardless, the website should probably capture the keys instead of letting that happen, I'm not well-versed in JS DOM events enough to know exactly what has to be changed, but, IIRC the callback function needs to return false.