OpenZeppelin Defender is a monitoring and automation platform launched by OpenZeppelin to provide infrastructure for smart contract security, automated responses, and operational workflows. Building within the OZ ecosystem, Defender offers teams a ground-up platform for managing their protocol security.

On June 6, 2025, the ALEX Protocol, a prominent Bitcoin-focused decentralized finance platform built on the Stacks blockchain, experienced a significant security breach. The exploit occurred due to a vulnerability in the protocol's self-listing verification logic, highlighting critical risks associated with decentralized finance (DeFi) and emphasizing the importance of secure permission management in smart contracts.

We break down the most critical DeFi exploits of 2025 so far, what went wrong, and what lessons must be internalized. Whether you’re a protocol founder, security lead, or community contributor this is for you.

If there’s one lesson from the last 3 years — and especially from Q1 2025 — it’s this: security can’t be a checkbox. Not anymore. Attackers no longer limit themselves to code. They target supply chains. They phish keys. They hijack admin roles. And they move faster than ever before.