OWASP ZAP

ZAP (Zed Attack Proxy) is the world’s most widely used open-source web application security scanner, functioning as a manipulator-in-the-middle proxy to intercept, inspect, and attack HTTP/S traffic between a browser and a target application. Originally created under OWASP, ZAP departed in 2023 to secure sustainable funding and is now maintained by its core development team with sponsorship from Checkmarx, while remaining an independent open-source project under the Apache 2.0 license.

ZAP’s discovery capabilities are particularly strong for modern web applications. A traditional link spider parses HTML to map application structure quickly, while a complementary AJAX spider drives a real browser to follow JavaScript-rendered navigation that conventional crawlers miss. Passive scanning monitors all proxied traffic without modification, flagging issues safely, while active scanning runs real attack payloads — XSS, SQL injection, Log4Shell, remote file inclusion — against targets to confirm vulnerabilities. ZAP supports authenticated scans, maintaining sessions throughout so that login-protected attack surface is fully covered.

What makes ZAP stand out is its dual identity as both an interactive security testing workbench and a headless automation engine. Security engineers can use the desktop GUI to manually probe requests in real time, while the same engine can be driven entirely via a REST API, YAML-based Automation Framework, or official Docker images — making it straightforward to embed continuous security scanning into CI/CD pipelines. This DevSecOps-friendly approach has made ZAP the default choice for organizations implementing shift-left security practices.