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Security testing Python Web applications

Your Web application written in Python works as intended, so you are done, right? But did you consider feeding in incorrect values? 16Gbs of data? A null? An apostrophe? Negative numbers, or specifically -1 or -231? Because that's what the bad guys will do – and the list is far from complete.

Handling security needs a healthy level of paranoia, and this is what this course provides: a strong emotional engagement by lots of hands on labs and stories from real life, all to substantially improve code hygiene. Mistakes, consequences, and best practices are our blood, sweat and tears.

The curriculum goes through the common Web application security issues following the OWASP Top Ten but goes far beyond it both in coverage and the details.

All this is put in the context of Python, and extended by core programming issues, discussing security pitfalls of the programming language.

So that you are prepared for the forces of the dark side.

So that nothing unexpected happens.




Training formats



3 days


1990 €

Target Group

Python developers working on Web applications


  • Getting familiar with essential cyber security concepts
  • Understanding Web application security issues
  • Detailed analysis of the OWASP Top Ten elements
  • Putting Web application security in the context of Python
  • Going beyond the low hanging fruits
  • Handling security challenges in your Python code
  • Identify vulnerabilities and their consequences
  • Learn the security best practices in Python


General Python and Web development

Course Content

Day 1

Cyber security basics

What is security?

Threat and risk

Cyber security threat types

Consequences of insecure software

The OWASP Top Ten

OWASP Top 10 – 2017

A1 - Injection

Injection principles

Injection attacks

  • SQL injection
  • SQL injection basics
  • Lab – SQL injection
  • Attack techniques
  • Content-based blind SQL injection
  • Time-based blind SQL injection

SQL injection best practices

  • Input validation
  • Parameterized queries
  • Additional considerations
  • Lab – SQL injection best practices
  • Case study – Hacking Fortnite accounts

Code injection

  • Code injection via input()
  • OS command injection
  • Lab – Command injection
  • OS command injection best practices
  • Avoiding command injection with the right APIs
  • Lab – Command injection best practices
  • Case study – Shellshock
  • Lab - Shellshock
  • Case study – Command injection via ping

Script injection

  • Server-side template injection (SSTI)
  • Lab – Template injection
  • Injection best practices

A2 - Broken Authentication

Authentication basics

Authentication weaknesses

Spoofing on the Web

Case study – PayPal 2FA bypass

Password management, Inbound password management

  • Storing account passwords
  • Password in transit
  • Lab – Is just hashing passwords enough?
  • Dictionary attacks and brute forcing
  • Salting
  • Adaptive hash functions for password storage
  • Password policy
  • NIST authenticator requirements for memorized secrets
  • Case study – The Ashley Madison data breach
  • The dictionary attack
  • The ultimate crack
  • Exploitation and the lessons learned
  • Password database migration
  • (Mis)handling None passwords

Day 2

The OWASP Top Ten

A2 - Broken Authentication

Password management

  • Outbound password management: Hard coded passwords, Best practices, Lab – Hardcoded password, Protecting sensitive information in memory, Challenges in protecting memory

Session management

  • Session management essentials
  • Session ID best practices
  • Why do we protect session IDs – Session hijacking
  • Session fixation
  • Session handling in Flask
  • Cross-site Request Forgery (CSRF): Lab – Cross-site Request Forgery, CSRF best practices, CSRF defense in depth, Lab – CSRF protection with tokens

A3 - Sensitive Data Exposure

Information exposure

Exposure through extracted data and aggregation

Case study – Strava data exposure

Error and exception handling principles

A4 - XML External Entities (XXE)

DTD and the entities

Entity expansion

Lab – Billion laughs attack

External Entity Attack (XXE)

  • File inclusion with external entities
  • Server-Side Request Forgery with external entities
  • Lab – External entity attack
  • Case study – XXE vulnerability in SAP Store
  • Preventing XXE
  • Lab – Using non-vulnerable parsers

A5 - Broken Access Control

Access control basics

Failure to restrict URL access

Confused deputy

  • Insecure direct object reference (IDOR)
  • Lab – Insecure Direct Object Reference
  • Authorization bypass through user-controlled keys
  • Case study – Authorization bypass on Facebook
  • Lab – Horizontal authorization

File upload

  • Unrestricted file upload
  • Good practices
  • Lab – Unrestricted file upload

A6 - Security Misconfiguration

Configuration principles

Python configuration best practices

  • Configuring Flask

A7 - Cross-site Scripting (XSS)

Cross-site scripting basics

Cross-site scripting types

  • Persistent cross-site scripting
  • Reflected cross-site scripting
  • Client-side (DOM-based) cross-site scripting
  • Lab – Stored XSS
  • Lab – Reflected XSS
  • Case study – XSS in Fortnite accounts

XSS protection best practices

  • Protection principles - escaping
  • XSS protection APIs in Python
  • XSS protection in Jinja2
  • Lab – XSS fix / stored
  • Lab – XSS fix / reflected
  • Additional protection layers
  • Client-side protection principles

A8 - Insecure Deserialization

Serialization and deserialization challenges

Deserializing untrusted streams

Deserialization with pickle

Lab – Deserializing with Pickle

Deserialization with PyYAML

Deserializing best practices

Day 3

The OWASP Top Ten

A9 - Using Components with Known Vulnerabilities

Using vulnerable components

Assessing the environment


Untrusted functionality import

Malicious packages in Python

Importing JavaScript

Lab – Importing JavaScript

Case study – The British Airways data breach

Vulnerability management

  • Patch management
  • Vulnerability management
  • Vulnerability databases

A10 - Insufficient Logging & Monitoring

Logging and monitoring principles

Insufficient logging

Plaintext passwords at Facebook

Logging best practices

Monitoring best practices

Web application security beyond the Top Ten

Client-side security

Same Origin Policy

  • Lab – Same-origin policy demo
  • Tabnabbing
  • Lab – Reverse tabnabbing

Frame sandboxing

  • Cross-Frame Scripting (XFS) attack
  • Lab - Clickjacking
  • Clickjacking beyond hijacking a click
  • Clickjacking protection best practices
  • Lab – Using CSP to prevent clickjacking

Common software security weaknesses

Input validation

Input validation principles

  • Blacklists and whitelists
  • Data validation techniques
  • Lab – Input validation
  • What to validate – the attack surface
  • Where to validate – defense in depth
  • How to validate – validation vs transformations
  • Output sanitization
  • Encoding challenges
  • Lab – Encoding challenges
  • Validation with regex
  • Regular expression denial of service (ReDoS)
  • Lab – Regular expression denial of service (ReDoS)
  • Dealing with ReDoS

Files and streams

  • Path traversal
  • Path traversal-related examples
  • Lab – Path traversal
  • Additional challenges in Windows
  • Virtual resources
  • Path traversal best practices
  • Format string issues

Unsafe native code

  • Native code dependence
  • Lab – Unsafe native code
  • Best practices for dealing with native code

JSON security

  • JSON injection
  • Dangers of JSONP
  • JSON/JavaScript hijacking
  • Best practices
  • ReactJS vulnerability in HackerOne

Wrap up

Secure coding principles

  • Principles of robust programming by Matt Bishop
  • Secure design principles of Saltzer and Schröder

And now what?

  • Software security sources and further reading
  • Python resources