[tbb-bugs] #27221 [Applications/Tor Browser]: Tor Browser 8.0a10 wants to update to 8.0a10

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#27221: Tor Browser 8.0a10 wants to update to 8.0a10
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 Reporter:  boklm                           |          Owner:  tbb-team
     Type:  defect                          |         Status:  new
 Priority:  Very High                       |      Milestone:
Component:  Applications/Tor Browser        |        Version:
 Severity:  Normal                          |     Resolution:
 Keywords:  ff60-esr, TorBrowserTeam201808  |  Actual Points:
Parent ID:                                  |         Points:
 Reviewer:                                  |        Sponsor:
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Comment (by mcs):

 For the record, this is easy to reproduce on macOS as well; simply follow
 the hint given in comment:10 (startup 8.0a9, shutdown, start again and
 apply the update).

 And it does seem to be a startupCache problem. Specifically, the problem
 disappears if I remove the file `TorBrowser-
 Data/Browser/Caches/*.default/startupCache/scriptCache.bin`.

 In fact, the wrong JS code is being executed. E.g., an update URL that
 contains `8.0a9` is generated and used even though
 `toolkit/modules/UpdateUtils.jsm` has a hard-coded (build- time) value of
 `8.0a10`.

 Kathy and I looked at the code and cannot determine where or how the
 script cache is invalidated. We did not find any evidence that individual
 entries (for individual files such as UpdateUtils.jsm) are invalidated; it
 looks like the entire cache is invalidated via
 `ScriptPreloader::InvalidateCache()` (see
 `js/xpconnect/loader/ScriptPreloader.cpp`).

 As far as we can tell, that `InvalidateCache()` method is only called in
 response to a `startupcache-invalidate` observer notification. But we
 don't see a place where that is generated after an update or if one were
 to install new bits over the top of an existing browser.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/27221#comment:13>
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