Bug 212049 – :is() / :where() parsing allows breaking shadow tree encapsulation

• Status: NEW
• Component: CSS

[Emilio Cobos Álvarez (:emilio)]

I'm adding some tests in https://bugzilla.mozilla.org/show_bug.cgi?id=1632647. But TLDR, these shouldn't probably parse, or if you disagree they probably shouldn't match:

  ::part(foo):is([attr='value'])
  :host(:is(div .foo))

[Ahmad Saleem]

Following WPT test was pushed as part of Mozilla bug: https://github.com/web-platform-tests/wpt/pull/23711/files

and we are only failing single test:

https://wpt.fyi/results/css/selectors/is-where-parsing.html?label=master&label=experimental&aligned&q=is-where-parsing.html

>>> Nested inside :host, with combinators

Don't know whether we have it as separate tracking or not but still adding 'BrowserCompat' and "WPTImpact' tags for future tracking.

[Radar WebKit Bug Importer]

<rdar://problem/122574812>