From Web2 Explorer to CodeHawks Eagle

0x539.eth discovered blockchain security through a link shared in a web2-focused community that gradually evolved into a hub for Bulgarian web3 researchers. 

Frustrated with the dwindling opportunities and rigid work setups in Bulgaria’s traditional tech scene, he found blockchain security more intellectually stimulating, better paid, and fully remote. That combination sealed it: he dove into blockchain development, hands-on practice, and community engagement with full focus. 

Within a year, he became a skilled smart contract auditor. Today, he and a close colleague formed ChainDefenders, a security team dedicated to protecting the web3 ecosystem.

0x539.eth’s story shows that comprehensive education, relentless practice, and collaborative problem-solving can fast-track success in blockchain security.

My path to smart contract security

My journey began in 2024 when a link was shared in a Discord community led by Krum Pashov, a recognized Bulgarian security researcher. His GitHub portfolio immediately caught my attention and pulled me into the world of blockchain security. Although I initially struggled to understand the vulnerabilities, something about the field resonated deeply.

I soon discovered Cyfrin Updraft and Patrick Collins's educational material. Immersing myself in Updraft’s courses, I studied Solidity, Foundry, and blockchain security. The learning curve was steep, but persistence and guile kept me moving forward.

After completing my initial studies, I teamed up with my friend PeterSR, and together, we participated in security contests on Sherlock and CodeHawks. Initially, we couldn’t spot any bugs, but eventually, we founded ChainDefenders, a company focused on finding smart contract vulnerabilities and mitigating them.

My computer science degree from Sofia University helped me understand cryptography and distributed systems. However, it was the specialized blockchain security education available on Cyfrin Updraft, combined with practical experience, that made the real difference.
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Why I became a security auditor

What drew me to auditing was a love for problem-solving and the satisfaction of making a real impact by protecting users and their assets. Discovering and fixing hidden vulnerabilities brings a deep sense of satisfaction since every protocol brings something unique, which keeps the work dynamic and deeply rewarding.

Through Cyfrin Updraft, I discovered CodeHawks, a platform that sharpened my skills through hands-on challenges. One unexpected benefit of auditing has been improving my communication skills. Writing vulnerability reports forces me to explain complex ideas clearly, succinctly, and accessibly, a vital skill in this field.
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Why security matters and my approach

Web3 is the future. A single flaw can trigger catastrophic losses, erode trust, and stall blockchain adoption. Depending on the protocol, smart contracts control millions or billions of dollars' worth of users' assets and sensitive data, making security an essential foundation, not an optional feature. 

Projects that skip thorough security reviews gamble with user funds and their reputation. Having witnessed how robust security practices can prevent costly exploits, I advocate for comprehensive audits, ongoing monitoring, and adhering to best practices such as formal verification. Investing in security early costs far less than repairing the damage caused by an exploit.
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Becoming a CodeHawks Eagle

My development as an auditor rests on three pillars: 

1. Hard work
2. Relentless curiosity
3. Community support

Cyfrin Updraft’s structured education was crucial in helping me navigate complex security concepts.

I started by studying "Mastering Ethereum" and completing several Updraft courses, including Foundry 101, Smart Contract Security, and Introduction to Python and Vyper. Then, I built real-world experience by competing in contests, analyzing vulnerabilities on Solodit, and learning from seasoned auditors.

After about a year of consistent study, hands-on practice, and refining my skills, I earned my place as a CodeHawks Eagle. Becoming an Eagle meant stepping into high-impact audits, working on cutting-edge projects, and joining a trusted network of top-tier security professionals who are shaping the future of blockchain security.

Even now, I never stop studying. I watch videos, review explanations of exploits, and dissect technical articles. Every audit is a fresh puzzle: a new protocol, a new attack vector. The constant challenge keeps the work exhilarating.
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The NFT bridge flaw that could have cost millions

Not every audit hands you a high-stakes bug, but this one did. While reviewing an ERC721Bridge contract, I spotted something that didn’t sit right. The protocol allowed users to bridge NFTs between chains, but it didn’t validate whether the token pairs were legitimate. No whitelist. No restrictions. Just blind trust.

I dug deeper.

What I found was startling. Anyone could take a cheap NFT from one chain and bridge it into a completely unrelated (and potentially far more valuable) NFT on another, as long as the protocol supported that token. In essence, it allowed attackers to swap junk for treasure.

To confirm my suspicion, I wrote test cases simulating these mismatched pairings. Both passed. Legitimate token pairs worked, as expected, but so did unrelated ones. There was no mechanism to stop it. The bridge had no idea whether the _localToken and _remoteToken were even meant to correspond. It just processed the transaction blindly.

The fix? Simple, yet vital. Implement a whitelist for ERC-721 pairs, just like the protocol already had for ERC-20 tokens. This one line of defense would ensure that only trusted pairings could move across the bridge.

This vulnerability stuck with me. It wasn’t about an obscure edge case or a convoluted math bug. It was a reminder that security often hinges on fundamentals: basic access control, consistent logic, and applying the same guardrails across features. Miss just one of those, and someone’s NFT collection could be gone in a flash.

This experience showed how minor oversights in access control can lead to significant security risks, especially in cross-chain interactions.
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What I wish I knew when starting out

If you’re stepping into blockchain security, think of it as entering a long, exhilarating marathon. It’s not a quick sprint.

Start by mastering the basics. Learn Solidity inside and out. Understand how blockchains really work. Build your foundation solid enough that you can spot cracks others miss.

Next, get your hands dirty. Participate in First Flights and public contests on CodeHawks. There’s no substitute for real-world practice. Every bug you find, every report you write, and every mistake you learn from will sharpen your instincts.

Don’t walk this path alone. Engage with the community on X (Twitter) and beyond. Ask questions. Share your discoveries. Surround yourself with builders and breakers who are as hungry to learn as you are. In web3 security, knowledge multiplies when shared.

Most importantly, stay relentless. Security work demands vigilance, creativity, and a constant hunger to get better. Every tough audit and unexpected bug is not an obstacle but a milestone in your growth.

Smart contract security isn’t just a technical challenge. It’s the defense line for the future of decentralized technology. If you're passionate, dive in. The path is tough, but the impact you can make is massive.

As Jefferson said, “Eternal vigilance is the price of liberty.” In blockchain security, it’s the price of freedom itself. And the future is counting on us to pay it.
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Looking forward

As the blockchain industry evolves, the need for strong security only grows. Through ChainDefenders and my personal work, I aim to strengthen the web3 ecosystem by identifying vulnerabilities early and helping teams build robust defenses.

If you're considering a career in this field, know that it welcomes newcomers who bring effort, focus, and a passion for protecting decentralized systems.

I’m just one message away if you need help getting started.