𝗦𝗲𝗰𝘂𝗿𝗶𝘁𝘆 𝗔𝘂𝗱𝗶𝘁 𝗥𝗲𝘀𝘂𝗹𝘁𝘀: 𝗪𝗵𝘆 𝗜 𝗳𝗲𝗹 𝗲𝗺𝗯𝗮𝗿𝗿𝗮𝘀𝘀𝗲𝗱
I recently ran a security audit on all my side projects. This includes my FastAPI backend, Telegram bots, PWA, and Streamlit apps.
I thought my code was safe because I was careful. I was wrong.
I am sharing these real production bugs to help you avoid them. These are not theoretical checklists. These are mistakes I actually made.
The Conditional Authentication Trap I wrote code that checked if an API secret existed before verifying it. If the environment variable was missing, the check skipped entirely. This meant my entire API was open to the public. Rule: If a secret is missing, fail hard with a 500 error. Never skip authentication.
The Git History Leak I once hardcoded an API key for a quick test. I moved it to a .env file later and thought it was fixed. But Git remembers everything. Anyone can find that key in my commit history. Rule: If you commit a key, assume it is stolen. Rotate it immediately. Use git-filter-repo to clean your history.
The Debug Endpoint Leak I left a /debug/config endpoint in production to help me troubleshoot. It exposed my database URLs and environment settings. Rule: Remove all debug endpoints before deployment. Use logs instead.
Leaking System Info via Errors I used str(e) in my error responses. This sent database errors and file paths directly to the user. Attackers use this to map your infrastructure. Rule: Log the detailed error for yourself. Send a generic "Internal Server Error" to the client.
The XSS Risk in Frontend I used innerHTML to render user content. This allowed scripts to run in other users' browsers. Rule: Always escape HTML. Treat innerHTML as a way to execute arbitrary code.
Missing Rate Limits I had endpoints that called expensive AI models without any limits. A single loop or a stolen key could cost me hundreds of dollars. Rule: Authentication stops unauthorized users. Rate limiting stops authorized users from abusing your system.
Permissive CORS Policy I used allow_origins=["*"] in production. This allows any site to make requests to your API. Rule: Only allow your specific frontend domain.
The Temporary File Leak If my code crashed while processing a file, the temporary file stayed on the disk forever. This wastes space and leaks sensitive data. Rule: Use try-finally blocks to ensure files are deleted even if an error occurs.
My new mandatory checklist:
Before coding: • Create a .gitignore • Create a .env.example
For every endpoint: • Add authentication • Use generic error messages • Add rate limits to expensive tasks
Before committing: • Scan for secrets in your diff
Before deploying: • Run security audits on your dependencies
Security issues do not happen by accident. They happen because of "TODO" comments and "temporary" fixes that stay in production forever.
Fixing a bug is boring. Fixing a breach is expensive.