User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:64.0) Gecko/20100101 Firefox/64.0 Steps to reproduce: Demo case here: https://codepen.io/dougstewart/full/QzdbxQ The blue area is a pseudo-element that is positioned outside the normal bounds of the button element. The styles are duplicated on an anchor tag. I verified this is also the case for non-pseudo-elements such as spans that have been positioned in the same way. Verified this behavior is unique to Firefox and appears to be macOS specific. Currently running macOS 10.14.2 (18C54). Actual results: When hovering over the blue area but not the orange area, the button does not trigger the hover styles but the anchor does. Expected results: The button's hover styles should trigger just like the anchor tag's.

Reproduced the issue on latest Beta and Release versions on MacOS 10.13. Works fine on the latest Nightly 66.0a1 (2018-12-23). There is probably a bug patch landed that fixed this issue on Nightly, not sure which tho