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Windows Registry UAC Bypass Attempt via Windows Media Player osk.exe AppCompatFlags

Identifies registry AppCompatFlags entries for Windows Media Player osk.exe that may indicate a UAC bypass attempt.

FreeReviewedSigma · High · v1
Product
windows
Category
registry_set
Author
Christian Burkard (Nextron Systems) (SigmaHQ), DRL 1.1
Published
2021-08-23
Updated
2026-07-30
AnalysisDetection

ATT&CK techniques

Priv Esc → Defense Evasion

  1. Recon

  2. Resource Dev

  3. Initial Access

  4. Execution

  5. Persistence

  6. Priv Esc

  7. Defense Evasion

  8. Cred Access

  9. Discovery

  10. Lateral Movement

  11. Collection

  12. C2

  13. Exfiltration

  14. Impact

What it detects

This rule flags registry writes that set the AppCompatFlags Compatibility Assistant store entry for Windows Media Player’s osk.exe path with a value of “Binary Data”. Attackers abuse these compatibility settings to influence how Windows launches executables and potentially bypass User Account Control protections. The detection relies on Windows registry set telemetry capturing the TargetObject path ending in the specified osk.exe Store location and the corresponding Details value.

Reporting behind it

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Windows Registry UAC Bypass Attempt via Windows Media Player osk.exe AppCompatFlags
Pivot detection · T1548.002 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.