My Windows Update Disables Firefox as Default Browser post was read by over ten thousand readers just here on the blog, and I can’t even follow secondary sources, as it got reposted in several other blogs, hit the front page of reddit …etc.
Best of all though was a private email inquiry I received from Gary Schare,Director, Internet Explorer Product Management at Microsoft. I gave him all the information I could, the MS team then tracked down the issue, and found that FireFox was still the default browser after the update, but it’s checking mechanism thought it wasn’t. Apparently the fix was on Mozilla’s side, and Microsoft and Mozilla have worked together in resolving the issue.
I have to say I find Microsoft attention, as well as the two organizations collaboration exemplary. The full story is best explained by quoting Gary verbatim – thanks for agreeing to it.
Thanks for providing the information on the updates you installed before experiencing the Firefox default browser prompt. We did a thorough investigation and have tracked down the cause of the issue. Before I explain the actual cause, I do want to let you know that we also determined that at no time did Firefox ever stop being the default browser on the machine. It mistakenly thought it was no longer the default and prompted users, but every entry point that triggered the default browser would still launch Firefox.
This issue is actually the result of a change in Firefox (added in Firefox v 126.96.36.199) and how it responds to Office changing a Windows registry key during the updating process. Whenever Office updates, it also verifies that many supporting registry keys are set to expected values (this is the same action that occurs when you use the “Detect and Repair” functionality in Office). The modification of registry keys during updating has happened throughout the lifecycle of Office 2003, and the Outlook Junk Email Filter delivered via Microsoft Update this month triggered this issue simply because it was the first update of Office since Firefox 188.8.131.52 became available, not because this specific update did anything differently.
On the basis of your report, the Office team has worked with Mozilla and believe they’ve arrived at an answer that will address the issue. The Mozilla folks have told us that the change will be in an upcoming version of Firefox, and it is tracked in this bug report on the Mozilla site. Thanks again for bringing this to our attention. Your blog was the trigger of the investigation and we’re all glad we were able to find the solution so quickly.”
Nicely done. Again, thanks for your attention and for fixing it.