🚨 Cracking the Clock: How I Took Over Any Account Using a Timestamp Leak

🧠 The Curiosity That Sparked It

It all started with a familiar feature: the “Forgot Password” flow. Simple, right? But sometimes, it’s the simplest features that hold the biggest security flaws.

I was testing a web application when I noticed something strange in its password reset mechanism. Most would have ignored it — but I decided to dig a little deeper.

🔍 The Flaw in the Reset Flow

Here’s how the functionality worked:

• When a user requested a password reset, the app sent them a reset link.
• This link contained a token, which was Base64-encoded.

• When decoded, the token revealed:
• The user’s email ID
• A timestamp (the time the reset was requested)

I intercepted this using Burp Suite, and here’s where it got interesting.

🕵️ Timing Is Everything

While observing the response headers, I noticed something weird.

• The timestamp inside the token was consistently 2 seconds behind the server’s response time header.
• This happened with multiple requests.

• In other words, the reset token was predictable, and I could reliably guess the token for someone else’s password reset link just by:
• Knowing their email address
• Calculating the timestamp close to real-time

🔓 Exploitation: Reset Anyone’s Password

I now had a plan:

1. I noted the current server time from the response headers.
2. I subtracted 2 seconds to match the format of the token’s timestamp.
3. I crafted my own Base64-encoded token using:

victim@example.com timestamp

4. I used this forged token in the password reset link.

Boom — access granted.

With just the victim’s email ID, I was able to:

• Generate a valid password reset token
• Reset their password
• Log into their account

No confirmation emails. No verification steps. Total Account Takeover.

💡 Lessons Learned

For Developers:

• Never trust client-side tokens — always sign or encrypt them.
• Avoid including guessable values like raw timestamps in tokens.
• Use proper randomness (e.g., UUID + HMAC or JWT with secret).
• Add rate limits and monitoring to sensitive endpoints.

For Hackers:

• Headers tell stories — pay attention to response times.
• A token isn’t secure just because it’s encoded.
• Subtle timing patterns can reveal powerful exploits.

🎯 Final Thoughts

This bug taught me that timing leaks aren’t just about performance — they can be security vulnerabilities too. When logic, predictability, and encoding come together in just the right (or wrong) way, they can open doors no one should walk through.

Stay curious. Stay ethical. And never underestimate the power of two seconds. 🕒