OWASP TimeGap Theory Handbook
A fun, CTF-style guide to TOCTOU vulnerabilities. Learn to spot and exploit web app race conditions using OWASP TimeGap Theory, with hands-on labs and a dinosaur-themed learning experience.
In this edition of Cyber Book Club, we’re highlighting the OWASP TimeGap Theory Handbook by Abhi M. Balakrishnan, an engaging, dinosaur-themed walkthrough that teaches one of the most overlooked security issues in web applications: TOCTOU (Time of Check to Time of Use) vulnerabilities.
First time seeing this?
If you’ve ever thought race conditions only apply to financial pages or that they’re too advanced for beginners, this book is for you. The handbook uses the OWASP TimeGap Theory project, a capture-the-flag (CTF) style open-source game, to teach readers how TOCTOU bugs work, how to find them, and how to exploit them ethically.
Whether you're just starting out in web application security or looking to sharpen your skills with real-world race condition testing, this book offers a practical, accessible, and even playful way to build expertise.
What You Will Learn
What TOCTOU vulnerabilities are and why they matter
How race conditions can be exploited in web apps
Step-by-step CTF-style walkthroughs using OWASP TimeGap Theory
Tools and techniques for identifying timing flaws
How to teach and share TOCTOU knowledge effectively
Who This Book Is For
This book is ideal for:
Beginner to intermediate web app security learners
CTF enthusiasts and ethical hackers
Bug bounty hunters looking for underexplored attack surfaces
Developers and testers learning secure coding practices
If you’ve been intimidated by race conditions or curious about timing-based vulnerabilities, OWASP TimeGap Theory Handbook makes learning TOCTOU practical, fun, and accessible.
Table of Contents (An Idea)
What Is a TOCTOU Vulnerability?
Understanding Race Conditions in Web Apps
Introduction to OWASP TimeGap Theory
Setting Up the CTF Environment
Exploiting Timing Issues Step-by-Step
Tools for Detecting TOCTOU Bugs
Writing Secure Code to Prevent Race Conditions
Teaching TOCTOU Concepts to Others
Lessons from the Field
Moving Beyond TimeGap: Next Steps in Web App Security