Created attachment 8878420 [details] screenshot of regression User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:54.0) Gecko/20100101 Firefox/54.0 Build ID: 20170613235745 Steps to reproduce: Added a background gradient to a table row with background-attachment: fixed. This has been working fine until Firefox 54. All platforms affected. See https://jsfiddle.net/qtkkokkt/1/ or attached files. Actual results: The background gradient renders incorrectly and bleeds out to the first parent container with a non-visible value for the overflow property. There are three different coloured rows - the colour of the last overrides the others and alpha is not applied. Expected results: Background gradient should be constrained to the table row and alpha should be applied.
Fixed in 55+. https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=33df8c04309cf792b214c5c6c903a391048f5516&tochange=0f95b12c599465afb36f64e268dd42bbbbafbfe1