The October Windows 11 update breaks Win32 edit controls in tabbed dialogues
• 2 min read
The October 2025 cumulative update for Windows 11 24H2 and 25H2 (KB5066835) came with an unfortunate bug for some Win32 apps: it makes multiline edit controls unusable in tabbed dialogue1 boxes that make proper use of theming.
More specifically, the bug happens when using
EnableThemeDialogTexture
with the ETDT_USETABTEXTURE flag on the parent of the edit control, as often
used in tabbed dialogue boxes in Win32 apps. (In such a scenario, the contents
of the tab is an embedded child dialogue, and that is the one that is the one
that gets the special background using EnableThemeDialogTexture to match the
tab control itself.)
Here’s a video of the bug in action in the Preferences window of the foobar2000 audio player2:
I also created a minimal standalone reproduction to demonstrate the problem.
This is functionality that had been working fine for decades (since Windows XP, to be precise). The problem appears to be that the edit control isn’t bothering to draw a background, and so existing text is not cleared when new characters are typed.
While normal Windows installations would have received the bug with the October cumulative update, the bug showed up before that in the KB5065789 preview update released at the end of September. That update does contain a few entries under the heading ‘[Input]’, though none of them sound like they should be related to the bug. (I’m more inclined to believe this was broken while Microsoft was working on Win32 dark mode, as they have seem to have been recently.)
The bug can be worked around in an affected application using the
WM_CTLCOLOREDIT window message,
and it has already
been worked around in a preview release of foobar2000.
I have not bothered to report this to Microsoft. The only avenue to report bugs is their Feedback Hub. Putting the fact that it’s a disorganised mess aside, I’m yet to experience anything positive from it (the opposite, in fact, when they do things like replace the title of your report with their response).
24 October 2025 update
Someone reported this bug on the Visual Studio developer community. The report currently has 21 votes and is marked as under investigation, so there’s some hope for it being fixed. (Note though that it’s not a bug in Visual Studio, it’s a bug in Windows.)