🔒 Fix IP Address Spoofing via X-Forwarded-For

[instax-dutta]

This PR fixes a security vulnerability where an attacker could spoof their IP address by providing a custom X-Forwarded-For header.

The previous implementation blindly trusted the first IP in the X-Forwarded-For list, which is often client-controlled. The new implementation prioritizes the X-Real-IP header (typically set by trusted infrastructure like Vercel) and falls back to the last IP in the X-Forwarded-For list, which is the most reliable entry in a proxy chain.

Key changes:

• Created src/lib/ip.ts for secure IP retrieval logic.
• Updated src/app/api/paste/route.ts to use the improved utility.
• Added src/lib/ip.test.ts with 6 test cases verifying the security and robustness of the fix.
• Removed the vulnerable code from src/lib/validation.ts.

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PR created automatically by Jules for task 8564156710181733307 started by @instax-dutta

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Project	Deployment	Actions	Updated (UTC)
binify	Ready	Preview, Comment	Mar 14, 2026 5:04pm

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 262e09ac-d0d8-4ee1-8e99-9a8d8d2ffdd5

📥 Commits

Reviewing files that changed from the base of the PR and between 6c75fd8 and 72c5363.

📒 Files selected for processing (4)

• src/app/api/paste/route.ts
• src/lib/ip.test.ts
• src/lib/ip.ts
• src/lib/validation.ts

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• Commit unit tests in branch security-fix-ip-spoofing-8564156710181733307

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