Closed Bug 1576246 Opened 3 months ago Closed 3 months ago

Set pref browser.urlbar.eventTelemetry.enabled by default


(Firefox :: Address Bar, task, P1, critical)




Firefox 70
70.4 - Aug 19 - Sep 1
Tracking Status
firefox-esr68 --- unaffected
firefox68 --- unaffected
firefox69 blocking verified
firefox70 + verified


(Reporter: adw, Assigned: adw)


(Blocks 1 open bug)



(2 files)

[Tracking Requested - why for this release]:

[Tracking Requested - why for this release]:

There's a bug (not yet filed) with how Firefox handles webextensions that set prefs that do not exist by default. My top-sites extension sets browser.urlbar.eventTelemetry.enabled to true. That pref doesn't exist by default. If I install the extension, restart Firefox, and then uninstall or disable the extension, the pref remains set to true. It should be cleared instead. In contrast, if I install the extension but do not restart before uninstalling or disabling, the pref is cleared.

This is a showstopper for the top-sites experiment that we want to run on 69.

Fortunately a safe and simple workaround is to simply set browser.urlbar.eventTelemetry.enabled by default, i.e., add browser.urlbar.eventTelemetry.enabled to browser/app/profile/firefox.js.

I talked with Ryan and he says it's not too late for RC.

Severity: normal → critical
Pushed by
Set pref browser.urlbar.eventTelemetry.enabled by default. r=harry
Attached patch Beta/69 patchSplinter Review

Beta/Release Uplift Approval Request

  • User impact if declined: Please see comment 0.
  • Is this code covered by automated tests?: No
  • Has the fix been verified in Nightly?: No
  • Needs manual test from QE?: No
  • If yes, steps to reproduce:
  • List of other uplifts needed: None
  • Risk to taking this patch: Low
  • Why is the change risky/not risky? (and alternatives if risky): This patch simply adds a default pref. The pref controls some extra quantumbar telemetry. The pref did not exist by default, and this patch sets it to false by default, which is functionally the same thing. Re: test coverage, we have a test that covers this pref; however, it only tests with the pref flipped on. So to be clear, we don't have automated test coverage for the pref's default state of false/non-existent. This is a trivial patch though, so I don't consider that to be a concern.
  • String changes made/needed: None
Attachment #9087839 - Flags: approval-mozilla-beta?
See Also: → 1576266
Closed: 3 months ago
Resolution: --- → FIXED
Target Milestone: --- → Firefox 70

Marking this in-testsuite+, but see the caveat in comment 3.

Flags: in-testsuite+


  1. Open about:config
  2. Search for browser.urlbar.eventTelemetry.enabled. It should be false.
  3. Open about:telemetry in a new tab and select the Events section. There shouldn't be any events with the category "urlbar".
  4. Open a new tab, type "test", and hit enter to do a Google search (or whatever your default engine is).
  5. Go back to the about:telemetry tab and refresh. Again, there shouldn't be any "urlbar" events.
  6. Go back to the about:config tab and set browser.urlbar.eventTelemetry.enabled to true.
  7. Repeat step 4.
  8. Go back to the about:telemetry tab and refresh. This time, there should be a "urlbar" event, method is "engagement", object is "enter", value is "typed".
  9. Go back to the about:config tab and set browser.urlbar.eventTelemetry.enabled to false.
  10. Repeat step 4.
  11. Go back to the about:telemetry tab and refresh. The urlbar event from step 8 should still be there, but no new urlbar events should be present.
Flags: qe-verify+
QA Whiteboard: [qa-triaged]
Comment on attachment 9087839 [details] [diff] [review]
Beta/69 patch

Set the pref by default to avoid incorrect behavior when running the experiment. Approved for 69.0rc1.
Attachment #9087839 - Flags: approval-mozilla-beta? → approval-mozilla-beta+

This is verified fixed on Firefox 70.a1 (latest) and 69.0b17 (from treeherder) using Windows 10x64, Windows 7x64, Ubuntu 18.04x64 and macOS 10.13.

Flags: qe-verify+
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