"@-moz-document url-prefix()" support dropped on Firefox 61

[laukstein]

@-moz-document url-prefix() doesn't work on Firefox 62+.
Tested on Firefox Nigthly build 62.0a1 (2018-05-13) (64-bit). Current stable v60 supports this media hack, not sure about v61.

For example @supports (-moz-appearance: meterbar) continues to work fine in Firefox Nigthly build 62.0a1.

Update: the support dropped on Firefox 61 due to security reasons [1].

[laukstein]

https://www.fxsitecompat.com/en-CA/docs/2018/moz-document-url-prefix-css-hack-will-no-longer-work/ just posted this Firefox change affecting Firefox 61.

Affecting @-moz-document url-prefix() CSS hack will no longer work

[browserstrangeness]

fyi: always test the final version (not just alpha/beta) before updating the site-- while a good portion of them fit the projected change, and this one probably does too, not everything makes it into the final release in the same fashion and the hacks sometimes are not affected. I have seen that occur on many occasions. Some even seem to work years after the css has been officially dropped. That said - this is really good investigative reporting people :)

[emilio]

FWIW, as much as I'd like to remove it, it only doesn't work on Nightly. layout.css.moz-document.url-prefix-hack.enabled is the preference that controls whether to allow @-moz-document url-prefix().

[emilio]

https://bugzilla.mozilla.org/show_bug.cgi?id=1449753 is the place where we'd disable it, should we deem it safe... But so far I don't think it is.

Also, I'd want to say that I've been a web developer, and that browser-specific hacks are an appeasing way to work around incompatibilities between browsers... But if you do find those incompatibilities, please do report them as a bug in the relevant engine! We can't fix everything instantly, but still keeping it on track and knowing which incompatibilities affect which people is really useful!

[browserstrangeness]

Interestingly enough this was actually not really intended to be a hack on moz's dev team. It was intended to be a new feature that never got included (nor probably even anything to do) with other browsers - but a firefox-only thing. It got removed only as a security measure because actual hackers found a way to use it for nefarious purposes.