CLASSIFIED // TOP SECRET
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TO: Joint Chiefs of Staff
FROM: Director of Cybersecurity Operations
SUBJECT: Zero-Day Exploit — Double Encoding Vector
Recent threat intelligence has identified a sophisticated exploitation
technique targeting web application firewalls. The attack vector uses
double URL encoding to bypass input filtering mechanisms.
Technical Details:
- Single-encoded payloads (%2e%2e%2f) are properly blocked by WAF
- Double-encoded payloads (%252e%252e%252f) bypass current detection
- The bypass relies on the WAF decoding once while the application
decodes a second time before processing the path
- Successful exploitation leads to Local File Inclusion (LFI)
Mitigation:
1. Apply filtering AFTER full input normalization
2. Implement allow-list based path validation
3. Deploy updated WAF signatures immediately