KB5078135: This OOB update includes quality improvements

January 24, 2026—KB5078135 (OS Build 26100.32236) Out-of-band

Improvements
This OOB update includes quality improvements. This update is cumulative and includes security fixes and improvements from the January 13, 2026, security update (KB5073379) and the out-of-band update (KB5077793) from January 17, 2026, in addition to the following:

• [File System] Fixed: After installing the Windows update released on and after January 13, 2026, some applications became unresponsive or encountered unexpected errors when opening files from or saving files to cloud-based storage, such as OneDrive or Dropbox. In certain Outlook configurations that store PST files on OneDrive, Outlook may hang and fail to reopen unless the process is terminated or the system is restarted. Users may also see missing sent Items or previously downloaded emails being re‑downloaded.

​​​​​If you installed earlier updates, your device downloads and installs only the new updates contained in this package.