Created attachment 8900076 [details] extensionslog.txt See the attached log for details (from extensions.logging.enabled=true). I was testing the updates for the click-to-play system addon, and there are two updates in the pipeline (bug 1390703 and bug 1390705). The version shipped with Firefox 55 is 1.2 I had a fresh profile which I used  to update to version 1.3. Then, on the same profile, I used  to update it to version 1.4. When doing this, I see in the log: Calling bootstrap method shutdown on version 1.3 Calling bootstrap method uninstall on version 1.3 Calling bootstrap method install on version 1.2 Calling bootstrap method startup on version 1.2 Calling bootstrap method shutdown on version 1.2 Calling bootstrap method uninstall on version 1.2 Calling bootstrap method install on version 1.4 Calling bootstrap method startup on version 1.4 URLs that can be used to do the same testing:  version 1.3: https://felipc.github.io/ctp25/update.xml  version 1.4: https://felipc.github.io/ctp100/update.xml
Hm. This is not the behavior I'd expect for sure... Felipe do you happen to know if this was a regression in 55 or is this an existing behavior? In any case, system add-ons rely on the behavior of the add-ons manager to override add-ons in lower-precedence install locations, it would be interesting to find out if this is something specific to the system add-on install location or if it happens elsewhere too. For instance if you install your add-on as a "normal" profile location add-on over the built-in one, do you see the same behavior? Or installing a temporary add-on over a normal one with the same add-on ID etc.
It's possible that I installed this addon as a regular addon once on this profile. I'll re-check with a new profile and report back (leaving the needinfo for now). I don't know if this is a regression in 55 or not. I don't recall seeing this in the past, but I'm also not sure if I've simulated an update on top of an update before.
What priority would you put on this Rob, something we need for 57?
FWIW I retested this to reproduce on a clean profile, and it still happens. (I didn't try to reproduce it on older versions). I'll note a message that seems relevant in the log, "Make addon app-system-defaults:email@example.com visible"
(In reply to Andy McKay [:andym] from comment #3) > What priority would you put on this Rob, something we need for 57? I'm not sure... I'd like to know if this is something that's always been there and we haven't noticed, or if it's a regression.
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