Web App Security: The OWASP Top 10 in Plain English

Web applications are a critical component of modern digital infrastructure, handling sensitive data and transactions. However, they remain vulnerable to various security threats. The Open Web Application Security Project (OWASP) has identified the top ten risks that web developers must address to ensure their applications are secure. This article breaks down these risks in plain English for engineers and product leaders.

1. Injection

Injection attacks occur when untrusted data is sent to an interpreter as part of a command or query. This can lead to malicious SQL, NoSQL, OS, or LDAP commands being executed on the server. To mitigate this risk, always parameterize input and use prepared statements in your code.

Examples

• A user inputs a crafted URL that executes arbitrary SQL queries against the database.

Using parameterized queries ensures that data is treated as literal values rather than executable code, preventing injection attacks.

2. Broken Authentication

Broken authentication can lead to unauthorized access and account hijacking. Weak or stolen credentials, improper session management, and lack of proper logout mechanisms are common issues here. Ensure that all sessions have a secure lifetime, use strong password policies, and properly invalidate sessions upon logout.

Examples

• A user's session token is compromised, allowing an attacker to access the user’s account.

Implementing strong password hashing and salting practices can prevent brute-force attacks. Additionally, using secure cookies with HttpOnly and Secure flags ensures that session tokens cannot be accessed by client-side scripts.

3. Sensitive Data Exposure

Sensitive data exposure occurs when sensitive information is not protected from unauthorized access. This includes passwords, credit card numbers, and personally identifiable information (PII). Implement strong encryption for sensitive data at rest and in transit using protocols like TLS.

Examples

• A web application stores plain-text passwords in its database.

To protect sensitive data, use hashing algorithms like bcrypt or Argon2 to securely store passwords. Employ encryption standards such as AES for data at rest and TLS 1.2+ for secure communication channels.

4. XML External Entities (XXE)

XML External Entity attacks exploit the processing of external entities in XML documents. Attackers can use XXE to steal server files, perform remote code execution, or inject malicious content into web applications. Disable external entity resolution and validate input to prevent these vulnerabilities.

Examples

• An application parses untrusted XML data without proper validation, allowing attackers to access sensitive files on the server.

Disabling external entities in XML parsers and validating all user inputs can mitigate XXE attacks. Regularly audit your code for any references to external entities that could be exploited.

5. Broken Access Control

Broken access control allows unauthorized users to access resources they should not have access to. This can lead to data theft, privilege escalation, and other security breaches. Implement role-based access controls (RBAC) and permission checks in your application logic.

Examples

• A user without administrative privileges is able to modify system settings due to a misconfigured RBAC.

To prevent broken access control, ensure that every action taken by a user is authorized. Use least privilege principles and regularly audit access controls to identify and fix any misconfigurations.

6. Security Misconfiguration

Security misconfigurations can occur at multiple levels, including server settings, APIs, and software components. Common issues include missing security headers, insecure default configurations, and unpatched software versions. Regularly update and harden your application’s configuration to minimize these risks.

Examples

• A web application uses default credentials for a database connection.

To secure your application, configure security headers like Content-Security-Policy (CSP) and X-Frame-Options. Keep all dependencies up to date with the latest security patches and follow best practices for server configuration.