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Cover image for 🔓 How Hackers Exploit Chrome Extensions for Free Trials—And How to Stop Them! 🕶️💻
Jackson Kasi
Jackson Kasi Subscriber

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🔓 How Hackers Exploit Chrome Extensions for Free Trials—And How to Stop Them! 🕶️💻

Intro: The Plot Twist No One Saw Coming

Picture this: You install a Chrome extension for a "14-day free trial." But what if I told you… I turned those 14 days into 7,978 years? 😱

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Spoiler: It’s easier than you think. Let’s spill the tea ☕ on how developers set up trials, how I “hacked” one, and how to stop folks like me!

NOTE: You can download the extension source code using this extension:

Extension Source Downloader


Part 1: How Free Trials Usually Work (aka “The Boring Stuff”)

Most developers track trials like this:

// When you install the extension...  
chrome.runtime.onInstalled.addListener(() => {
  chrome.storage.local.set({ installDate: Date.now() }); // 🗓️
});

// Later, they check if you’re broke & need to pay 💸  
chrome.storage.local.get(["installDate"], (result) => {
  const trialEnd = result.installDate + (14 * 86400000); // 14 days in ms
  if (Date.now() > trialEnd) {
    alert("Trial over! Give us money NOW."); // 😤
  }
});
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Translation: They save the day you installed it and nag you after 14 days. Classic.

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Part 2: How I Became a Trial Wizard 🧙‍♂️ (Thanks, DeepSeek!)

So, I peeked into the extension’s code (don’t try this at home, kids 🚫). But let’s be honest, I’m too lazy to manually sift through messy JavaScript files. 😴 Instead, I used DeepSeek, an AI model designed for digging through code and finding loopholes like a pro. 💀

Step 1: Pass the Code to DeepSeek

I uploaded the JavaScript file (the bundled code) and simply prompted DeepSeek with something like:

“Analyze this code for vulnerabilities or ways to bypass trial expiration logic.”

DeepSeek quickly spotted the key section of code responsible for managing the trial period:

chrome.storage.local.set({ installDate: Date.now() });  
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Step 2: Time Travel, But for Code

DeepSeek also suggested a sneaky modification:

“You can replace Date.now() with a future timestamp to extend the trial indefinitely.”

So, I followed the advice and tweaked the code to:

chrome.storage.local.set({ 
  installDate: new Date('9999-12-31').getTime() // ⏳
});
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The Result?

The extension now thought I installed it on December 31, 9999🤣.

That means it calculated the trial expiration date as millions of days into the future, effectively giving me a never-ending trial. 🏝️

Thanks to DeepSeek, I didn’t even have to break a sweat combing through the code! 😅

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Why This Works: The Secret Sauce 🍝

Let’s make this fun and interactive! Here's a simplified breakdown of why my little time-travel trick worked:


The Extension’s Original Brain 🧠

When you install the extension, it thinks:

“Okay, let’s save today’s date and track when 14 days are up.”

  1. Step 1: The Install Date 🗓️ The code saves the current date in milliseconds:
   chrome.storage.local.set({ installDate: Date.now() });
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Translation: “Hey, they installed this on January 28, 2025. Write that down!”

  1. Step 2: Trial Expiry Logic 💣 Every time you use the extension, it calculates if the trial is over:
   chrome.storage.local.get(['installDate'], (result) => {
       const trialEndDate = result.installDate + (14 * 24 * 60 * 60 * 1000); // 14 days in ms
       if (Date.now() > trialEndDate) {
           alert("Your trial has ended. Please upgrade.");
       }
   });
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Translation: “Today is February 11, 2025. Hmm… did 14 days pass since January 28, 2025? Yup? Time to ask for $$$!”


My “Hack” Logic: Future Me Is Clever 🕶️

Instead of letting the extension record today’s date, I gave it a wild date way in the future:

chrome.storage.local.set({ installDate: new Date('9999-12-31').getTime() });
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Here’s why this fooled it:

  1. Step 1: New Install Date 🛸

    By telling the extension that I installed it on December 31, 9999, it believed this fake date without question.

  2. Step 2: Expiry Logic Becomes a Joke 🤣

    When it checked for the trial expiration, it did this:

   const daysLeft = (installDate + trialPeriod - Date.now()) / 86400000;
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Here’s how the math worked:

  • Install Date: 253,402,300,799,000 ms (December 31, 9999).
  • Trial Period: Add 14 days → irrelevant because the install date is already ridiculous.
  • Today’s Date: 1,730,084,800,000 ms (January 28, 2025).

The calculation:

   const daysLeft = (253,402,300,799,000 - 1,730,084,800,000) / 86400000;
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Result? 2,912,783 days left in the trial. That’s 7,978 years!

  1. The Extension’s Reaction 🤯 “Oh, cool! The trial’s still valid… and will be for the next few millennia!”

Well, you’ve done it 👏

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Why This Is So Silly 😂

By giving the extension a fictitious install date in the future, I effectively bypassed its simple logic. It trusted the installDate without questioning whether it made sense.


Lesson for Developers: Trust Issues Are Good 😅

If your extension relies on client-side storage to manage trials, it’s like leaving your door unlocked in a neighborhood full of curious hackers. 🏚️ Always validate your logic with server-side checks and encryption!

Stay tuned for ways to keep sneaky wizards like me at bay. 🧙‍♂️💀


Part 3: How to Stop Sneaky Hackers Like Me 🛑

Developers, don’t panic! Here’s how to protect your trial:

1. Server-Side Checks (aka “Stop Trusting Browsers!”) 🌐

Store install dates on YOUR server, not the user’s browser:

// On install, ping your server  
fetch('https://your-api.com/trial', {
  method: 'POST',
  body: JSON.stringify({ userId: 'UNIQUE_ID', installDate: Date.now() })
});
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Pro Tip: Add a setInterval to check the server daily. No more funny business!

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2. Encrypt the Install Date 🔐

Turn installDate into gibberish with CryptoJS:

const encryptedDate = CryptoJS.AES.encrypt(
  Date.now().toString(), 
  'SuperSecretKey123' // 🕵️♂️
);
chrome.storage.local.set({ installDate: encryptedDate.toString() });
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Hackers: “Is this… Spanish??” 😵

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3. Obfuscate Your Code (Make It Unreadable) 🤯

Use tools like JavaScript Obfuscator to turn:

chrome.storage.local.set({ installDate: Date.now() });  
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Into:

var _0x44020f=_0xe31d;function _0x5aa4(){var _0x113da9=['storage','local','26PGlJXt','12NVzeFQ','197296ESbWxY','137768wmlklv','3645515rhHAQx','7167171ZYajOo','7940184eINQOh','6AOUSNv','3huOqcq','189zrpgHD','126MZIqID','2459272XcgHUX','6WRHEFk','115780ldQySt'];_0x5aa4=function(){return _0x113da9;};return _0x5aa4();}function _0xe31d(_0x1826f8,_0x68a104){var _0x5aa47b=_0x5aa4();return _0xe31d=function(_0xe31d1,_0x3a8241){_0xe31d1=_0xe31d1-0x175;var _0x164585=_0x5aa47b[_0xe31d1];return _0x164585;},_0xe31d(_0x1826f8,_0x68a104);}(function(_0x3811c6,_0x2d46f9){var _0x361065=_0xe31d,_0x46812e=_0x3811c6();while(!![]){try{var _0x31a7c6=parseInt(_0x361065(0x176))/0x1*(parseInt(_0x361065(0x17c))/0x2)+parseInt(_0x361065(0x182))/0x3*(-parseInt(_0x361065(0x175))/0x4)+parseInt(_0x361065(0x17e))/0x5*(-parseInt(_0x361065(0x181))/0x6)+-parseInt(_0x361065(0x183))/0x7*(parseInt(_0x361065(0x17d))/0x8)+-parseInt(_0x361065(0x184))/0x9*(parseInt(_0x361065(0x177))/0xa)+parseInt(_0x361065(0x17f))/0xb*(parseInt(_0x361065(0x17b))/0xc)+parseInt(_0x361065(0x17a))/0xd*(parseInt(_0x361065(0x180))/0xe);if(_0x31a7c6===_0x2d46f9)break;else _0x46812e['push'](_0x46812e['shift']());}catch(_0x3f6589){_0x46812e['push'](_0x46812e['shift']());}}}(_0x5aa4,0x634fd),chrome[_0x44020f(0x178)][_0x44020f(0x179)]['set']({'installDate':Date['now']()}));
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Hackers: “Is this code or hieroglyphics?!” 🐍

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4. Fingerprint Their Device 🖨️

Use FingerprintJS to tie the trial to their device:

FingerprintJS.load().then(fp => fp.get()).then(result => {
  const fingerprint = result.visitorId; // Unique to their browser
  // Store fingerprint + installDate on your server
});
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Result: If they reinstall, you’ll KNOW. 👀😂

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Conclusion: Don’t Let Hackers Win!

Client-side trials are like leaving your car unlocked in a sketchy neighborhood 🚗💨. Use server checks, encryption, and fingerprints to keep your extension safe!

Ethical Note: This post is for laughs and learning—not a hacking manual! Always respect developers’ hard work. 🌟

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Thanks for reading! Now go forth and build unhackable trials. 🛠️

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Retry later

Top comments (2)

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jacksonkasi profile image
Jackson Kasi • Edited

Exactly! Validating on the backend makes it much harder to bypass. Front-end validation alone is too easy to exploit and leaves everything exposed

I’ve explored many front-end-based extensions, and most have vulnerabilities. Recently, I found one popular extension with this exact loophole:

chrome.storage.local.set({ installDate: Date.now() });  
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I wrote this article to share the fun and spread awareness. :)

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