Web Security for Developers: Password Hashing, HTTPS, and Common Vulnerabilities

Introduction

Web security is not optional — it is a fundamental requirement for every application that handles user data, processes sensitive information, or provides services online. As a developer, understanding common vulnerabilities and security best practices is as important as knowing how to write clean code.

This guide covers the essential security concepts every web developer should understand, from password storage to common attack vectors. We also explain the security advantages of client-side processing — the approach our tools use to keep your data safe.

Password Security

Passwords remain the primary authentication mechanism for most web applications, and how you store them is one of the most critical security decisions you will make.

Never Store Plaintext Passwords

This seems obvious, but plaintext password storage still occurs in production systems. If an attacker gains access to your database (through SQL injection, a misconfigured backup, or an insider threat), plaintext passwords are immediately compromised for every user.

The impact extends beyond your application because users frequently reuse passwords across multiple services. A breach of your user database with plaintext passwords can lead to cascading compromises across banking, email, social media, and other accounts.

Password Hashing

The correct approach is to hash passwords using a purpose-built password hashing function. Hashing is a one-way mathematical function that converts a password into a fixed-length string that cannot be reversed. When a user logs in, you hash the provided password and compare it to the stored hash — if they match, the password is correct.

Critically, you must use a password-specific hashing algorithm like bcrypt, scrypt, or Argon2 — NOT general-purpose hash functions like SHA-256 or MD5. General-purpose hashes are designed to be fast, which is exactly what you do not want for password hashing. Fast hashing means an attacker can try billions of passwords per second in a brute-force attack.

Password hashing algorithms like bcrypt are deliberately slow (configurable via a work factor), making brute-force attacks impractical. They also incorporate a unique random salt for each password, preventing rainbow table attacks and ensuring that identical passwords produce different hashes.

Password Strength

Our Password Generator tool creates cryptographically random passwords using the Web Crypto API. Unlike Math.random(), which is predictable, the Web Crypto API provides true randomness suitable for security-sensitive applications.

Strong passwords should be at least 12 characters long, include uppercase and lowercase letters, numbers, and special characters, and avoid dictionary words, personal information, and common patterns. Better yet, use a password manager to generate and store unique passwords for every service.

HTTPS and Transport Security

HTTPS encrypts all communication between the browser and server, preventing eavesdropping, tampering, and impersonation. Without HTTPS, anyone on the same network (a coffee shop WiFi, a corporate network, an ISP) can read every request and response in plaintext.

How HTTPS Works

HTTPS uses TLS (Transport Layer Security) to establish an encrypted channel. The process begins with a handshake where the server presents its certificate, the client verifies the certificate against trusted certificate authorities, and both parties agree on encryption keys.

After the handshake, all data transmitted between client and server is encrypted with symmetric encryption (fast) using keys established during the handshake with asymmetric encryption (secure key exchange). The result is that even if someone intercepts the network traffic, they see only encrypted gibberish.

HTTPS Is Now Required

Modern browsers flag HTTP sites as "Not Secure" in the address bar, which erodes user trust. Google uses HTTPS as a ranking signal for search results. Many modern web APIs (geolocation, camera, microphone, service workers) are only available on HTTPS pages. There is simply no valid reason to serve any website over HTTP in 2026.

Free certificates from Let's Encrypt and automatic HTTPS from platforms like Vercel, Netlify, and Cloudflare have eliminated the cost and complexity barriers that once made HTTPS adoption difficult.

Cross-Site Scripting (XSS)

XSS occurs when an attacker injects malicious scripts into web pages viewed by other users. The injected script runs in the context of the victim's browser, with access to cookies, session tokens, and page content.

Types of XSS

Reflected XSS occurs when user input is immediately reflected in the page response without proper encoding. For example, a search page that displays your search query without escaping HTML could execute injected JavaScript.

Stored XSS occurs when malicious input is stored in the database and displayed to other users. A comment containing a script tag, if not properly sanitized, would execute for every user who views the page.

DOM-based XSS occurs when client-side JavaScript manipulates the page DOM using untrusted data, such as URL parameters or user input, without proper sanitization.

Preventing XSS

The primary defense is output encoding — converting special characters like less-than signs, greater-than signs, quotes, and ampersands to their HTML entity equivalents before inserting user data into the page. Modern frameworks like React, Angular, and Vue do this automatically for most cases, but developers must be aware of dangerous patterns like dangerouslySetInnerHTML in React.

Content Security Policy (CSP) headers provide a second layer of defense by restricting which scripts can execute on your page. A strict CSP prevents inline scripts and limits script sources to your own domain, making injected scripts unable to execute.

Cross-Site Request Forgery (CSRF)

CSRF tricks authenticated users into performing unintended actions. If a user is logged into their bank and visits a malicious page, that page could contain a hidden form that submits a transfer request to the bank. Because the user's browser automatically includes their session cookie with the request, the bank processes it as a legitimate action.

Preventing CSRF

CSRF tokens are the standard defense. Each form includes a unique, server-generated token that the server validates on submission. Since the attacker cannot predict the token, they cannot craft a valid forged request.

SameSite cookie attributes provide additional protection by preventing cookies from being sent with cross-origin requests. Setting SameSite to Lax or Strict prevents the browser from including session cookies in requests initiated by other sites.

SQL Injection

SQL injection occurs when user input is inserted directly into SQL queries without proper parameterization. An attacker can manipulate the query to access unauthorized data, modify records, or even execute operating system commands.

Preventing SQL Injection

The solution is parameterized queries (also called prepared statements). Instead of concatenating user input into SQL strings, you use placeholders that the database driver fills in safely. This ensures that user input is always treated as data, never as SQL code.

ORMs like Prisma, Sequelize, and SQLAlchemy use parameterized queries by default, providing protection against SQL injection without requiring developers to think about it explicitly. However, raw query escape hatches in ORMs can reintroduce the vulnerability if used carelessly.

Client-Side Processing: Our Security Approach

Our tools use a fundamentally different security model than traditional web applications. Instead of uploading your files to a server for processing, all conversion, compression, and calculation happens directly in your browser.

This approach eliminates several entire categories of risk. Your files never leave your device, so there is no risk of server-side data breach, no network interception risk, and no data retention to worry about. There are no uploaded files sitting on a server that could be accessed by unauthorized parties.

This is possible because modern browsers provide powerful APIs — Canvas for image manipulation, Web Crypto for hashing and encryption, ArrayBuffer for binary data processing, and Web Workers for parallel computation. These APIs enable sophisticated processing entirely within the browser environment.

Conclusion

Web security is a shared responsibility between developers, platform providers, and users. Understanding the common vulnerabilities covered in this guide — and their defenses — is essential for building trustworthy web applications. Remember that security is not a feature you add at the end; it is a mindset that informs every design and implementation decision throughout the development process.