The release of Windows 10 build 10240 to Windows Insiders was the last preview build before "Release To Manufacture" (RTM). However, that doesn't mean the Windows team is done working on it. Microsoft has been releasing fit and finish updates since the build was released. Today, Microsoft has released another "hotfix" update, announced by Gabe Aul on Twitter:
Another hotfix rollup (KB3074674) now available for #WindowsInsiders running build 10240 on Windows Update.
— Gabriel Aul (@GabeAul) July 21, 2015
There's no documentation or blog post yet to indicate what the "hotfix rollup" does, but it will install automatically via Windows update in the next day or so. Alternatively, Windows 10 Insiders can install the update immediately via "Check for updates".
The updates for Windows 10 Insider build 10240 are arriving quickly as Microsoft patches things up for an RTM release due date of July 29. After RTM Windows Insiders will continue to receive new builds and updates for the next Windows version while regular Windows 10 users will have a choice of how fast they want the updates to arrive with Slow and Fast rings.