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Fixing Cloudflare 521 Error with Nginx Configuration - Turn Off Windows Defender Real-Time Protection for Speed-Troubleshooting Error 0x800f081f in Windows Update

Updated 2026-06-13 13:08:46windows-fixes
Fixing Cloudflare 521 Error with Nginx Configuration - Turn Off Windows Defender Real-Time Protection for Speed-Troubleshooting Error 0x800f081f in Windows Update
Likely symptom
Likely cause
Safe rollback

Verification route

  • Repeat the original action, not only a simplified test case.
  • Restart the app or reload the service after configuration changes.