Building Custom Slither Detectors to Catch DeFi Access Control Flaws Before Attackers Do

The biggest smart contract security failures of early 2026 haven't been classic reentrancy bugs or integer overflows — they've been access control misconfigurations . Authorization abuse, compromised privileged access, and missing role checks have collectively cost protocols hundreds of millions. Yet most audit toolchains still focus primarily on the "classic" vulnerability classes. In this hands-on guide, we'll build four custom Slither detectors specifically designed to catch the access control patterns that have led to real DeFi exploits. These aren't toy examples — they're production-ready detectors you can drop into your CI pipeline today. Why Access Control Deserves Its Own Tooling According to BlockSec's February 2026 security roundup, authorization-related losses accounted for over 60% of total DeFi losses that month. The OWASP Smart Contract Top 10 for 2026 lists "Access Control Vulnerabilities" as the #1 risk category. The problem isn't that developers don't know about onlyOw