[tbb-bugs] #34305 [Applications/Tor Browser]: NoScript inconsistent behaviour in Firefox 77 (currently beta)

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#34305: NoScript inconsistent behaviour in Firefox 77 (currently beta)
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 Reporter:  acat                                 |          Owner:  acat
     Type:  defect                               |         Status:
                                                 |  needs_information
 Priority:  Medium                               |      Milestone:
Component:  Applications/Tor Browser             |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  noscript TorBrowserTeam202005,       |  Actual Points:
  ff78-esr                                       |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by ma1):

 Sorry for the late answer, but I was unable to comment (the textarea was
 missing).
 As correctly guessed by acat, the culprit isan implementation detail of
 https://bugzilla.mozilla.org/show_bug.cgi?id=1462989 (a webRequest
 listener can only either delete or merge CSP headers now, not both in the
 same callback), which combined to the fact CSP headers injected by
 extensions get cached by the browser and automatically reinserted in
 cached responses, can cause all sorts of confusions when policies change
 without cache-purging reloads.
 The (quite annoying, but effective) work-around is uniquely "tagging"
 NoScript's CSP headers, to not interfere with page's own policies or other
 extensions (something NoScript already did) and registering a second
 auxiliary listener which just does the cleanup by removing the previously
 cached  CSP headers.

 I hope to release a development build containing this work-around later
 today or tomorrow, and a stable AMO auto-update within this week.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/34305#comment:6>
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