User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:75.0) Gecko/20100101 Firefox/75.0

Steps to reproduce:

I created an html element with a :hover rule. I then added javascript that moved the button when clicked. If I didn't move my mouse after clicking, the :hover rule was still aplied. Here is a codepen that shows the bug: https://codepen.io/limabeanbloom/pen/KKpLeGp

Actual results:

The :hover rule was still applied until I moved my mouse

Expected results:

The :hover rule should not have been applied because the element had moved and the mouse was no longer hovering over it.

I can reproduce on Windows10 Nightly76.0a1 and Chrome80 as well.

The priority flag is not set for this bug.
:mattwoodrow, could you have a look please?

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Because this bug's Severity has not been changed from the default since it was filed, and it's Priority is -- (Backlog,) indicating it has has not been previously triaged, the bug's Severity is being updated to -- (default, untriaged.)