It's starting to seem like Microsoft can't update anything without breaking it. Windows Latest reported yesterday that Windows Defender, the built-in antivirus tool for Windows 10, stopped functioning properly after it was updated recently.
The report indicated that Windows Defender--which is set to be renamed Microsoft Defender as it expands to additional platforms--has shown an error message to multiple Windows 10 users. Windows 7 and 8 users don't appear to be affected.
That error message reads: "Items skipped during scan. The Windows Defender Antivirus scan skipped an item due to exclusion or network scanning settings." Either those scans are failing, or the error message is being shown when it shouldn't be.
Failed scans could potentially expose Windows 10 users to security risks. An incorrect error message could also erode trust in Windows Defender, though, which might lead Windows 10 users to install antivirus software they probably don't need.
Luckily it seems like Windows Defender's offline scans are working as intended, so Windows 10 users should probably use that option until this problem is resolved. Microsoft explained how to use Windows Defender offline in a support article.