Security is not a separate job that happens after the code is written — it is part of writing good code. You do not need to become a penetration tester, but every developer should understand the most common ways applications get compromised, and how to prevent them.

Never Trust User Input

The single most important rule in application security: treat every input as potentially hostile. Validate and sanitise data on the server, use parameterised queries to prevent SQL injection, and escape output to stop cross-site scripting (XSS).

"Most breaches do not require genius-level attacks. They exploit basic mistakes that careful developers could have prevented."

— ThinkCraft Security Faculty

Encrypt Everything in Transit

HTTPS is non-negotiable. Encrypting traffic protects credentials, tokens, and personal data from being intercepted. Combine it with secure cookie settings and proper handling of secrets, and never log sensitive information in plain text.

Get Authentication and Authorization Right

Authentication proves who a user is; authorization decides what they are allowed to do. Use well-tested libraries rather than rolling your own, hash passwords with a strong algorithm, and always check permissions on the server — never rely on the UI to hide what a user should not access.

Keep Dependencies Up to Date

A huge share of vulnerabilities come from outdated third-party packages. Audit your dependencies regularly, apply security updates promptly, and remove libraries you no longer use. Automated tooling can flag known issues before they reach production.

Learn the OWASP Top 10

The OWASP Top 10 is the industry-standard list of the most critical web application risks. Reading through it — and understanding how each risk applies to your own code — is one of the highest-value things a developer can do for security.