portswigger.net/research· Jan 28, 2025

Bypassing character blocklists with unicode overflows

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Unicode codepoint truncation - also called a Unicode overflow attack - happens when a server tries to store a Unicode character in a single byte. Because the maximum value of a byte is 255, an overflo
🎯 Vulnerability: Web Security Vulnerability
💡 Defense Fix: Implement strict input validation, contextual output encoding, and enforce least-privilege authorization controls.