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URL encoding and decoding are fundamental processes in web security and development, especially when handling user input, crafting payloads, or working with URLs containing special characters. URL encoding ensures that special characters, which might be interpreted incorrectly by browsers or web servers, are properly encoded for safe transmission. Conversely, URL decoding converts encoded characters back to their readable form.





In this form, you can either encode text into a URL-safe format or decode URL-encoded text back to its original characters. This tool is essential for penetration testers, web developers, and anyone working with URLs to ensure that data can be securely and accurately transmitted in web requests, APIs, and HTTP headers.





Key Features:





    

  • Encode: Converts special characters into URL-encoded format (e.g., spaces to %20, ampersands to %26).
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  • Decode: Converts URL-encoded characters back into their human-readable form.
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  • Command Output: Provides a Python command for encoding or decoding, which you can run directly from your terminal.
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  • Interactive: The form dynamically updates as you input text to encode or decode, showing the corresponding Python command and result in real-time.
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Why URL Encoding Matters for Penetration Testers:





As penetration testers, you often need to craft malicious URLs for testing, such as in Cross-Site Scripting (XSS) or SQL Injection attacks. URL encoding helps obfuscate payloads to evade detection by web filters and security mechanisms. Understanding URL encoding is essential for manipulating URLs, performing directory traversal attacks, and creating more complex test cases.





Common URL Encodings and Their Use Cases:





    

  1. Basic Encoding:

      

    • Space: Encoded as %20
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    • Ampersand (&): Encoded as %26
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    • Equals sign (=): Encoded as %3D
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    • Question mark (?): Encoded as %3F
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    • Forward Slash (/): Encoded as %2F
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    • Colon (:): Encoded as %3A
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  2. Reserved Characters in URLs: Certain characters are reserved in URLs, including the question mark (?), ampersand (&), equal sign (=), and others. These characters are used in query strings to separate parameters. If these characters are part of data being sent, they should be encoded to prevent them from being misinterpreted.
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  3. Handling Non-ASCII Characters: Characters outside the ASCII range, such as é, ç, or even emoji characters like 😀, are often URL-encoded to ensure they can be safely transmitted over the internet. URL encoding ensures that non-ASCII characters are converted to their percent-encoded form (e.g., é becomes %C3%A9).
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  4. Common URL Encoding in Pen Testing:

      

    • XSS Payload Encoding: When testing for XSS, you may need to encode <, >, and quotes (") to avoid triggering security mechanisms while sending malicious payloads in URLs.
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    • SQL Injection Attack Encoding: Attackers may encode ', ", or -- to evade filters in URL-based SQL injection attacks.
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    • Directory Traversal Encoding: Pen testers will often encode ../ as %2E%2E%2F to test for vulnerabilities in web applications’ path handling.
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Common URL Encoding and Decoding Options:





    

  • encode: Encode special characters into their percent-encoded equivalents to safely send data over the web.
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  • decode: Decode URL-encoded characters back into their original form for easier analysis and interpretation.
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Examples of URL Commands:





Encoding Example:





    

  • Input: Hello World! How's it going?
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  • Command:
    > python -c "import urllib.parse; print(urllib.parse.quote('Hello World! How\'s it going?'))"
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  • Output: Hello%20World%21%20How%27s%20it%20going%3F
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Decoding Example:





    

  • Input: Hello%20World%21%20How%27s%20it%20going%3F
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  • Command:
    > python -c "import urllib.parse; print(urllib.parse.unquote('Hello%20World%21%20How%27s%20it%20going%3F'))"
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  • Output: Hello World! How's it going?
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Encoding Example with Special Characters (XSS Test Payload):





    

  • Input: <script>alert('XSS')</script>
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  • Command:
    > python -c "import urllib.parse; print(urllib.parse.quote('<script>alert(\'XSS\')</script>'))"
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  • Output: %3Cscript%3Ealert%28%27XSS%27%29%3C%2Fscript%3E
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Encoding Example for SQL Injection:





    

  • Input: 1' OR '1'='1
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  • Command:
    > python -c "import urllib.parse; print(urllib.parse.quote('1\' OR \'1\'=\'1'))"
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  • Output: 1%27%20OR%20%271%27%3D%271
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Encoding Example with Non-ASCII Characters:





    

  • Input: Café Brûlé
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  • Command:
    > python -c "import urllib.parse; print(urllib.parse.quote('Café Brûlé'))"
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  • Output: Caf%C3%A9%20Br%C3%BBl%C3%A9
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Decoding Example for Directory Traversal:





    

  • Input: %2E%2E%2F%2E%2E%2F%2E%2E%2Fetc%2Fpasswd
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  • Command:
    > python -c "import urllib.parse; print(urllib.parse.unquote('%2E%2E%2F%2E%2E%2F%2E%2E%2Fetc%2Fpasswd'))"
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  • Output: ../../../../etc/passwd
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Result Output:





You can see the result of the encoding or decoding process directly in the output section. It will also generate the corresponding Python command, which you can use for further operations, pen testing, or save for your reference.





Practical Use Cases for Penetration Testers:





    

  • XSS Testing: Encode script tags or JavaScript payloads and use them in URL parameters to test for cross-site scripting vulnerabilities.
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  • SQL Injection: Encode SQL injection payloads to test web applications’ vulnerability to SQL injection.
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  • Command Injection: Use URL encoding to send payloads in HTTP requests that might bypass filters for remote command execution.
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  • Obfuscation: Use URL encoding to obfuscate URLs for testing purposes, making it harder for automated defenses to detect potentially malicious inputs.
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