BurpSuite Response Modification Rules to Bypass Client-Side Controls

Client-side security controls are often implemented to restrict user input, but they can be easily bypassed using tools like BurpSuite. Below are five powerful response modification rules to bypass common client-side restrictions:

1. Unhide Hidden Form Fields – Developers often hide sensitive fields to prevent tampering.
2. Highlight Unhidden Fields – Visually distinguish hidden fields for easier manipulation.
3. Enable Disabled Form Fields – Bypass “read-only” or disabled input restrictions.
4. Remove Input Field Length Limits – Override frontend character restrictions.
5. Remove JavaScript Form Validation – Disable client-side checks for XSS, SQLi, or DoS payloads.

You Should Know: Practical Implementation

1. Unhiding Hidden Fields

Use BurpSuite’s “Match and Replace” rule to modify HTML responses:
– Rule: Replace `type=”hidden”` with `type=”text”`
– BurpSuite Steps:
– Go to Proxy → Options → Match and Replace
– Add a new rule:

Match: type="hidden" 
Replace: type="text" 

2. Highlighting Unhidden Fields

Modify CSS to make hidden fields visible:

• Rule: Inject CSS to highlight modified fields:

  <style>input[type="text"][name="secret"] { border: 2px solid red !important; }</style>
  

3. Enabling Disabled Fields

Remove `disabled` and `readonly` attributes:

• Rule: Replace `disabled=”disabled”` with ` ` (empty)
• BurpSuite Rule:

  Match: disabled="disabled" 
  Replace: 
  

4. Removing Input Length Limits

Bypass `maxlength` restrictions:

• Rule: Remove `maxlength` from input fields:

  Match: maxlength="[0-9]+" 
  Replace: 
  

5. Disabling JavaScript Validation

Prevent client-side validation scripts from executing:

• Rule: Comment out validation functions:

  // Replace: if (validateForm()) { ... } 
  // With: if (true) { ... } 
  

What Undercode Say

Client-side security is never enough—always enforce server-side validation. Use these BurpSuite tricks to test applications, but ensure backend protections are robust.

Expected Output:

• Modified HTTP responses with client-side restrictions removed.
• Visible hidden fields, enabled inputs, and bypassed JS checks.
• Successful exploitation of weak client-side controls.

Related Course: Weekly Pentest Tips & Tricks (125+ lessons)

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References:

Reported By: Aaandrei %F0%9D%90%82%F0%9D%90%A8%F0%9D%90%AE%F0%9D%90%A7%F0%9D%90%AD%F0%9D%90%A5%F0%9D%90%9E%F0%9D%90%AC%F0%9D%90%AC – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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