Microsoft Faces New Windows 0-Day Exploit Following Record Security Patches

On July 15, 2026, a researcher published exploit code that enables low-privilege Windows accounts to make changes to administrator accounts. This release coincided with Microsoft issuing a record number of security patches, addressing 570 vulnerabilities. The exploit, known as HiveLegacy, targets a flaw in the Windows User Profile Service, allowing users with limited rights to compromise an admin user's account by modifying its registry hive. The researcher, who operates under the pseudonym NightmareEclypse, has previously disclosed nine exploits and has expressed concerns regarding Microsoft's handling of bug reports. The proof-of-concept code was modified to reduce the risk of malicious use.