If you have ever run Windows Defender's Offline Scan, your BitLocker encryption may already be compromised — before an attacker even logs in.
Security researcher Chaotic Eclipse, the same anonymous figure behind the RoguePlanet Defender zero-day dropped just 24 hours earlier, has now published a second unpatched exploit. This one, dubbed GreatXML, bypasses BitLocker — Windows' built-in full-disk encryption that is supposed to keep your data locked even if someone physically steals your machine or boots from external media.
An accidental four-hour discovery
What makes GreatXML particularly striking is how it was found. The researcher described it plainly: "This was an accidental discovery; it took a total of 4 hours to find this." No months-long audit, no sophisticated toolchain — just a stumbled-upon flaw that renders one of Windows' most trusted security features essentially decorative.
The root trigger is the Windows Defender Offline Scan feature — a built-in tool millions of users have run at least once to clean deeply embedded malware. Running that scan leaves the machine in a state that GreatXML can exploit.
How it works
The exploit is straightforward to execute for anyone with brief physical access to a target machine:x.`
- Copy two XML files —
unattend.xmlandRecovery/WindowsRE/ReAgent.xml— to the root of the machine's recovery partition (a small, separate partition Windows uses for repair and recovery tools). - Reboot into WinRE (Windows Recovery Environment) by holding Shift and clicking Restart.
If the victim machine ever ran Defender Offline Scan, the result is a shell with unrestricted access to the BitLocker-encrypted volume — without entering the BitLocker PIN or recovery key.
Chaotic Eclipse acknowledges a nuance: if Offline Scan was never run, triggering the bug requires either logging in to initiate it first or finding a way to boot into WinRE in an offline scan state without credentials. The researcher believes the latter is achievable.
GreatXML is not Chaotic Eclipse's first time cracking BitLocker open. Their earlier exploit, YellowKey (CVE-2026-45585), was patched by Microsoft this week as part of the June 2026 Patch Tuesday update — just as GreatXML was publicly disclosed and left unpatched.
The back-to-back releases — RoguePlanet (Defender LPE to SYSTEM) one day, GreatXML (BitLocker bypass) the next — paint a concerning picture. An attacker combining both could escalate local privileges and then access fully encrypted volumes on the same machine, with no patch currently available for either.
The broader context remains the same: Chaotic Eclipse alleges Microsoft dismissed their vulnerability reports, revoked their MSRC portal access, and refused to compensate them. Microsoft has condemned the uncoordinated releases but has not assigned a CVE to GreatXML as of publication.
What you can do now
There is no patch. Until Microsoft responds:
- Avoid leaving machines unattended in environments where physical access cannot be controlled.
- Disable or restrict WinRE access on sensitive enterprise machines where possible.
- Do not treat BitLocker alone as sufficient protection on high-value devices until this is resolved.
- Watch for a CVE assignment and apply the patch as soon as it becomes available.