I can reliably recreate this in the Windows Sandbox. This issue goes away if normal (NSIS) Firefox is set to default before MSIX is set to default. It also returns if the Settings app is used to change the default browser. Digging in further, just running the relevant `reg.exe delete ...` gives the same error. Given this context I think we're hitting a permissions issue that for some reason impacts file associations but not url associations. Given this context I'm not sure there's much to do here. It's likely preferable to allow the url association change, but still pop open the Settings deep link for the user to set other file associations. :nalexander thoughts on how to proceed here?
Bug 1863980 Comment 4 Edit History
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I can reliably recreate this in the Windows Sandbox on Windows 11. This issue goes away if normal (NSIS) Firefox is set to default before MSIX is set to default. It also returns if the Settings app is used to change the default browser. Digging in further, just running the relevant `reg.exe delete ...` gives the same error. Given this context I think we're hitting a permissions issue that for some reason impacts file associations but not url associations. Given this context I'm not sure there's much to do here. It's likely preferable to allow the url association change, but still pop open the Settings deep link for the user to set other file associations. :nalexander thoughts on how to proceed here?
I can reliably recreate this in the Windows Sandbox on Windows 11. This issue goes away if normal (NSIS) Firefox is set to default before MSIX is set to default. It also returns if the Settings app is used to change the default browser. Digging in further, just running the relevant `reg.exe delete ...` gives the same error. Given this context I think we're hitting a permissions issue that for some reason impacts file associations but not url associations. I guess that would apply to explorer.exe as that is the context reg.exe is launched under. Given this context I'm not sure there's much to do here. It's likely preferable to allow the url association change, but still pop open the Settings deep link for the user to set other file associations. :nalexander thoughts on how to proceed here?
I can reliably recreate this in the Windows Sandbox on Windows 11. This issue goes away if normal (NSIS) Firefox is set to default before MSIX is set to default. It also returns if the Settings app is used to change the default browser. Digging in further, just running the relevant `reg.exe delete ...` gives the same error. Given this context I think we're hitting a permissions issue that for some reason impacts file associations but not url associations. I believe this permission issue would apply to explorer.exe as that is the context reg.exe is launched under. Given this context I'm not sure there's much to do here. It's likely preferable to allow the url association change, but still pop open the Settings deep link for the user to set other file associations. :nalexander thoughts on how to proceed here?
I can reliably recreate this in the Windows Sandbox on Windows 11. This issue goes away if normal (NSIS) Firefox is set to default before MSIX is set to default. It also returns if the Settings app is used to change the default browser. Digging in further, just running the relevant `reg.exe delete ...` gives the same error. Given this context I think we're hitting a permissions issue that for some reason impacts file associations but not url associations. I believe this permission issue would apply to explorer.exe as that is the context reg.exe is launched under, iiuc for both Firefox MSIX and from Powershell. Given this context I'm not sure there's much to do here. It's likely preferable to allow the url association change, but still pop open the Settings deep link for the user to set other file associations. :nalexander thoughts on how to proceed here?