My phone was updated to Fennec 54.0a2 this morning via Google Play. It would appear we haven't frozen updates off Aurora for them?

That was supposed to be the case. Johan?

TL;DR: We can't revert back to 53.0a2. No new aurora will be published, until new relman says so. Thanks for noticing it. I see what happened. We have a machine [1] that waits until a new aurora nightly is created and publishes it, no matter of the tree status. I just turned it off. We haven't seen this issue before because tc-migration happened in Aurora 53. That worker wasn't fully active at the time of Aurora 52. The short term solution is done ([1] is turned off). We need to put it back on when Aurora is signed off. The middle term solution is to add this step in the mergeduty documentation[2]. I'll handle that The long term one: Put that task in the aurora nightly graph. Aki suggested a to add decision task that checks whether the trees are closed. This requires bug 1317783. [1] https://dashboard.heroku.com/apps/fennec-aurora-task-creator [2] https://wiki.mozilla.org/ReleaseEngineering/Merge_Duty/Steps

Per release-drivers, updates can now be offered on the Aurora channel. I reactivated fennec-aurora-task-creator.