I'm curious how you were running the installer that this showed up. I reproduced it when installing with the stub installer, but not when directly using the 84.0.1 full installer, which made me wonder whether the issue was related to the full installer not having elevated itself. Running the full installer directly from an administrator command prompt also causes the failure. So I suspect the elevation is involved here somehow. I added a log entry to record the working directory, it records the install directory in both success and failure cases. I'll poke around a bit more, but I'm not sure what's going on here. I agree it's worth looking into using the redistributable, but that might want to be a separate bug.
Bug 1683425 Comment 1 Edit History
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I'm curious how you were running the installer that this showed up. I reproduced it when installing with the stub installer, but not when directly using the 84.0.1 full installer, which made me wonder whether the issue was related to the full installer not having elevated itself. Running the full installer directly from an administrator command prompt also causes the failure. So I suspect the elevation is involved here somehow. I added a log entry to record the working directory, it records the install directory in both success and failure cases. I'll poke around a bit more, but I'm not sure what's going on here. I agree it's worth looking into using the redistributable installer, but that might want to be a separate bug.