User Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36 Steps to reproduce: Reference Chrome bug: http://crbug.com/879428 Firefox has inconsistent behavior for choosing which ancestor to stick to when overflow:hidden is involved. For the simple case, Firefox aligns with both Chrome and Safari in always choosing the overflow:hidden ancestor - observe http://output.jsbin.com/yaxovep across all three browsers. However, if the overflow:hidden ancestor is a table-cell, Firefox ignores it and chooses the viewport (or next ancestor scroller) as the ancestor to attach the sticky to. See the left-hand column in https://codepen.io/AlexRad/pen/XMQpvq. This behavior was observed on Firefox Nightly, but I believe it applies to stable as well.

Mozilla/5.0 (X11; Linux x86_64; rv:64.0) Gecko/20100101 Firefox/64.0 (20180910100056) I've tested this report on Windows 10 x64 and Ubuntu 18.04 x64 using the latest Nightly and Fx release build. I was able to reproduce the mentioned behavior using the provided test pages. When scrolling table content I would expect the green box in the first column not to stick. In competitor browser, this is handled properly.

This might just be a version of bug 221154, which indicates that 'overflow' on table cells has some known issues.