The security researcher going by the name Chaotic Eclipse (aka INFINITE NIGHTMARE, MSNightmare, and Nightmare-Eclipse) has released a proof-of-concept (PoC) for a new Microsoft zero-day called ShieldBreak. The vulnerability, rooted in Microsoft Defender for Windows, demonstrates a patch bypass for CVE-2026-50656 (CVSS score: 7.8), otherwise known as RoguePlanet. Although it was first disclosed by the researcher in June 2026, a patch for the vulnerability was not released by Microsoft until almost a month later. ShieldBreak, on the other hand, is assessed to be a full patch bypass for CVE-2026-50656, with the researcher claiming that "Microsoft has failed to properly patch the RoguePlanet vulnerability." "Improper link resolution before file access ('link following') in Windows User Profile Service allows an authorized attacker to elevate privileges locally," Microsoft said.