[tbb-bugs] #29246 [Applications/Tor Browser]: WebGL is sometimes blocked outright instead of put behind a click-to-play placeholder

[Tor Bug Tracker & Wiki]

#29246: WebGL is sometimes blocked outright instead of put behind a click-to-play
placeholder
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 Reporter:  gk                                   |          Owner:  tbb-
                                                 |  team
     Type:  defect                               |         Status:  new
 Priority:  Medium                               |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  noscript, tbb-usability-website,     |  Actual Points:
  TorBrowserTeam201903, GeorgKoppen201903,       |
  tbb-8.5-must-alpha                             |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by gk):

 Replying to [comment:1 gk]:
 > FWIW, to reproduce this bug you have to set `webgl.disable-extensions`
 to `false`. By default we disable those extensions and I guess in that
 case the behavior is okay-ish in the sense that the website is saying
 "Your browser does not support WebGL" and no click-to-play placeholder
 shows up.
 >
 > However, this happens even if the necessary extensions are allowed and
 going in the NoScript menu and enabling WebGL there shows the demo in that
 scenario.

 Alright, I bisected the problem and the first bad version is 10.1.9, and
 more exactly 10.1.9rc1.

 ma1: Can you please have a look? This reproduces easily in a vanilla
 Firefox 60 ESR with the following steps:

 1) Create a clean, new profile and install NoScript 10.1.9rc1.
 2) Make sure everything but WebGL is allowed in NoScript's settings menu
 3) Go to https://demo.marpi.pl/biomes/
 4) Expected outcome: Click-to-play placeholders (as in 10.1.8.23)
 5) Actual outcome: No click-to-play placeholders

 I guess we found out about that so late because we had WebGL not working
 at all in Tor Browser 8 at the beginning.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/29246#comment:8>
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