Bugzilla

(In reply to Francesco Lodolo [:flod] from comment #1)
> I still need to check if 77 is affected. If it is, on the next update an existing language pack will be considered compatible, and things will break very badly.

This bug is not tied to a Firefox version, but to whether AMO has a known match for the requested version.

I just tried to simulate an update for updating from 77 to 78, by replacing "79.0a1" with "78.0" (and "78.0.112") in the URL from comment 10, and am served a langpack for the correct target (78.0).

https://versioncheck.addons.mozilla.org/update/VersionCheck.php?reqVersion=2&id=langpack-fr@firefox.mozilla.org&version=77.0buildid20200504222419&maxAppVersion=77.*&status=userEnabled,incompatible&appID=%7Bec8030f7-c20a-464f-9b0e-13a3a9e97384%7D&appVersion=78.0.112&appOS=Linux&appABI=x86_64-gcc3&locale=en-US&currentAppVersion=78.0.112&updateType=49&compatMode=normal

(In reply to Francesco Lodolo [:flod] from comment #1)
> I still need to check if 77 is affected. If it is, on the next update an existing language pack will be considered compatible, and things will break very badly.

This bug is not tied to a Firefox version, but to whether AMO has a known match for the requested version.

I just tried to simulate an update for updating from 77 to 78, by replacing "79.0a1" with "78.0" (and "78.0.112") in the URL from comment 10, and am served a langpack for the correct target (78.0).

https://versioncheck.addons.mozilla.org/update/VersionCheck.php?reqVersion=2&id=langpack-fr@firefox.mozilla.org&version=77.0buildid20200504222419&maxAppVersion=77.*&status=userEnabled,incompatible&appID=%7Bec8030f7-c20a-464f-9b0e-13a3a9e97384%7D&appVersion=78.0.112&appOS=Linux&appABI=x86_64-gcc3&locale=en-US&currentAppVersion=78.0.112&updateType=49&compatMode=normal

PS. [Update check is triggered here](https://searchfox.org/mozilla-central/rev/027893497316897b8f292bde48dbb6da2391a331/toolkit/mozapps/extensions/internal/XPIInstall.jsm#2045-2057) and the [min/max versions are overwritten during the update check](https://searchfox.org/mozilla-central/rev/027893497316897b8f292bde48dbb6da2391a331/toolkit/mozapps/extensions/internal/XPIInstall.jsm#2817-2829).