Don't Trust JWT Headers: Algorithm Confusion Attacks Explained
Learn how JWT algorithm confusion attacks work in Python. Understand none algorithm bypass, RS256 to HS256 substitution, and how to prevent these authentication vulnerabilities with secure PyJWT …
OWASP A01: Broken Access Control Prevention Guide
Stop broken access control attacks that affect 94% of applications. Complete guide covering IDOR, privilege escalation, SSRF, and prevention strategies with real code examples.
OWASP Top 10 2025 Developer Guide
Master the OWASP Top 10 2025 web application vulnerabilities. Complete developer guide with supply chain failures, exceptional conditions, and modern security risks.
OWASP A02: Security Misconfiguration Guide 2025
Master security misconfiguration prevention with this comprehensive guide. Learn why A02 jumped to #2 in OWASP 2025, real attack scenarios, and framework-specific hardening techniques.
Python SSRF Prevention Guide [2026]
Master SSRF prevention in Python applications. Complete guide with Flask, Django, FastAPI examples, URL validation, cloud protection, and production testing. Stop server-side request forgery attacks.
CSRF vs SSRF: Developer Guide [2026]
Master the differences between CSRF and SSRF attacks. Complete comparison with examples, prevention strategies, and code samples. Essential guide for web developers securing applications.
AppSec.fyi Hits 2,200+ Resources: What's New
AppSec.fyi has grown to a full application security reference platform with 2,241 resources across 24 categories, weekly newsletter, and glossary.
MCP Tool Poisoning: Hidden Attack Surface
MCP tool descriptions are an attack surface. Malicious servers can embed hidden instructions to exfiltrate SSH keys and hijack agent behavior.
csp-toolkit: CSP Header Analysis at Scale
I built csp-toolkit — a Python library and CLI for parsing, analyzing, and finding bypasses in Content Security Policy headers. Latest: violation-report fix suggestions, patched CSP drafts, and …
Use-After-Free: Classic Memory Corruption Guide
Use-after-free vulnerabilities are among the most dangerous memory corruption bugs. Learn what they are, how they work, and how to find them.
CVE-2026-27696: SSRF in changedetection.io
Real-world SSRF vulnerability analysis: How CVE-2026-27696 bypassed URL validation in changedetection.io to access AWS metadata. Includes PoC, timeline, and prevention strategies. CVSS 8.6.
AppSec.fyi: Curated Security Resources
I built AppSec.fyi as a curated collection of application security resources organized by vulnerability class — a go-to reference for security professionals.
Secure Python Applications Guide [2026]
Essential Python security guide for developers. Stop SSRF, SQL injection & XSS attacks with practical code examples, security libraries, and testing tools. Complete 2026 checklist included.
Understanding HTTP Request Smuggling Attacks
HTTP Request Smuggling exploits parsing discrepancies between front-end and back-end servers to inject hidden requests. Learn how it works and how to defend against it.
7 Critical SSRF Attack Techniques [2026]
Master SSRF attack vectors with real-world examples. Learn how attackers exploit server-side requests to access AWS metadata, internal services, and sensitive data. Includes detection methods.
SSRF Prevention Guide [2026]
Stop SSRF attacks before they steal your AWS credentials. Complete prevention guide with Python/Node.js code, real exploit examples, and enterprise defense strategies.
What is the Common Weakness Enumeration (CWE)?
Complete guide to CWE (Common Weakness Enumeration) - MITRE's standardized system for classifying 900+ software vulnerabilities. Essential for developers, security teams, and compliance.
XXE Injection Payloads for Security Testing
A collection of common XXE (XML External Entity) injection payloads for security testing, with notes on how each exploits vulnerable XML parsers.
Content Security Policy Complete Guide [2026]
Master Content Security Policy implementation to stop XSS attacks. Practical CSP examples, bypass prevention, testing tools, and security headers. Complete developer guide with code samples.