Your C: drive mysteriously filling up? July's update finally kills the bug behind it

If your free space has been vanishing for months with nothing obvious to blame, you may have met one of the stranger Windows 11 bugs of the year. A single hidden system file - CapabilityAccessManager.db-wal - was quietly growing without limit on affected PCs. On one machine it hit 332GB; another user got 276GB back after clearing it. On the worst-hit systems it could swell to around 500GB.

That file is meant to be tiny. It's a log of apps asking for permission to use your camera, microphone, location or screen. Because of a fault introduced back in early 2026, it kept writing without ever tidying up after itself. It was widespread, too - in one 10,000-device survey, well over half the machines had the file bloated past a gigabyte. Microsoft acknowledged it publicly on June 29 and has now shipped the fix in this month's update, KB5101650.

Want to know if you were caught? Open Settings > Storage, expand Show more categories, and look under System & reserved. A healthy version of that file sits at a couple of megabytes; if that category looks bloated by gigabytes, you were affected - and installing the July update stops it growing further. In rare cases where the giant file lingers after patching, a restart usually lets Windows clear it.

The lesson is a familiar one: install the monthly updates, because they fix far more than just security holes. Tendvane's check-for-updates confirms the July build actually installed rather than quietly failing, and its Health score keeps an eye on your free disk space so a runaway file like this shows up before your drive fills.