A Windows 10 Cumulative Update broke Edge Developer Tools and no-one noticed

Edge is only used by about 4% of desktop web browsers, which may explain why when a recent Windows 10 Cumulative Update broke its developer tools hardly anyone noticed, until today that is.

On the 24th October Microsoft released Cumulative Update KB4462933 for Windows 10 April 2018 Update, then with no known issues.  WindowsLatest reports that Microsoft has now updated the Support entry for the update, adding two new issues, one of which is that Edge Developer Tools may no longer function.

The entry reads:

Developer Tools (F12) may fail to start in Microsoft Edge.

Using Administrator permissions, delete the following files and restart Developer Tools:

On an x64 machine: C:\Windows\SystemApps\Microsoft.MicrosoftEdgeDevToolsClient_8wekyb3d8bbwe\microsoft.system.package.metadata\Autogen\JSByteCodeCache_64

On an x86 machine: C:\Windows\SystemApps\Microsoft.MicrosoftEdgeDevToolsClient_8wekyb3d8bbwe\microsoft.system.package.metadata\Autogen\JSByteCodeCache_32

Microsoft is working on a resolution and will provide an update in an upcoming release.

As Microsoft notes, a proper fix will likely come on Patch Tuesday next week.

The second issue is a bit more esoteric, and Microsoft can be forgiven for missing it. However, unlike the first, there is no workaround. That reads:


After you install the August Preview of Quality Rollup or September 11, 2018 .NET Framework update, instantiation of SqlConnection can throw an exception. For more information about this issue, see the following article in the Microsoft Knowledge Base:

4470809 SqlConnection instantiation exception on .NET 4.6 and later after August-September 2018 .NET Framework updates


Microsoft is working on a resolution and will provide an update in an upcoming release.

Likely not too many people are dependent on Edge Developer Tools working, but it does bring to question the throroughness of Microsoft’s testing once again if such an obvious issue is missed.

See the Support entry for KB4462933  here.

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