In Special:Preferences, it is possible to click a checkbox through the disabled "Save" button, meaning it's easy to (un)tick a box by accident. Hard to screenshot this bug but perhaps someone can screen capture.
Related Gerrit Patches:
|mediawiki/core : master||Update OOUI to v0.30.2|
|oojs/ui : master||WikimediaUI theme: Prevent z-index leaks for radios and checkboxes|