The Most Common Code Security Issues

The Most Common Code Security Issues – And How to Prevent Them

he Most Common Code Security Issues – And How to Prevent Them
In an age where software drives business, code security has become a core concern—not just for security engineers, but for every developer writing a single line of code. From high-profile breaches at Equifax to the infamous Log4j vulnerability, we’ve seen how a single weak link in code can compromise entire systems.

This article provides an in-depth analysis of the most common security vulnerabilities in software development today, complete with real-world examples and practical mitigation strategies.

 
1. SQL Injection
SQL Injection (SQLi) is one of the oldest and most dangerous application security risks. It allows attackers to manipulate queries to extract or corrupt database information.

🔍 How it Works:
When user input is embedded directly into a SQL query without validation or escaping, malicious input can break the syntax and execute arbitrary SQL.

💣 Real-World Example:
In 2009, Heartland Payment Systems, a major payment processor, was breached via SQL Injection. Over 130 million credit card records were stolen, costing the company over $140 million in fines and damages.

✅ Prevention:
Use prepared statements (e.g., PreparedStatement in Java, or parameterized queries in Python’s psycopg2)
Avoid dynamic SQL string building
Sanitize and validate all input, especially from forms and APIs
java

// Bad (vulnerable)
String query = "SELECT * FROM users WHERE username = '" + input + "'";

// Good (safe)
PreparedStatement ps = conn.prepareStatement("SELECT * FROM users WHERE username = ?");
ps.setString(1, input);

 
2. Cross-Site Scripting (XSS)
XSS vulnerabilities let attackers inject malicious scripts into web pages viewed by other users. This can steal session tokens, redirect users, or manipulate the DOM.

🔍 How it Works:
An attacker crafts input that includes HTML/JavaScript code. If the input is reflected or stored without sanitization, the script runs in the victim’s browser.

💣 Real-World Example:
In 2011, a persistent XSS attack on Twitter allowed attackers to auto-retweet and spread malware through user interactions.

 Prevention:
Escape all user content rendered in HTML (&, <, >, etc.)
Use frameworks that auto-sanitize (React, Angular)
Set HTTP headers like Content-Security-Policy
javascript
CopyEdit
// Vulnerable: rendering raw input
document.body.innerHTML = "<div>" + userComment + "</div>";

// Safe: escape before rendering or use DOM methods
const div = document.createElement("div");
div.innerText = userComment;
document.body.appendChild(div);

 
3. Cross-Site Request Forgery (CSRF)
CSRF tricks users into submitting actions they didn’t intend while logged in, such as changing passwords or initiating money transfers.

🔍 How it Works:
Attackers host a malicious site that silently sends requests to another site where the user is authenticated.

💣 Real-World Example:
In 2008, a CSRF vulnerability in Netflix allowed attackers to change account settings by luring users to click a malicious link.

Prevention:
Implement anti-CSRF tokens (e.g., @CsrfToken in Spring Security)
Use SameSite=Strict cookie attributes
Validate Referer or Origin headers
 
4. Broken Authentication
Broken or weak authentication mechanisms can allow attackers to impersonate users or access sensitive accounts.

🔍 How it Works:
Developers might store plaintext passwords, fail to lock out brute-force attempts, or mishandle session tokens.

💣 Real-World Example:
In 2012, LinkedIn suffered a breach exposing 117 million passwords, many stored using unsalted SHA-1 hashes.

 Prevention:
Store passwords using bcrypt or Argon2
Implement account lockout after repeated failures
Use secure session cookies (Secure, HttpOnly, SameSite)
Enforce Multi-Factor Authentication (MFA)
 
5. Insecure Deserialization
This vulnerability allows attackers to execute code by passing crafted objects during deserialization.

🔍 How it Works:
In Java, deserializing untrusted input with ObjectInputStream can lead to remote code execution (RCE) if the input contains malicious payloads.

💣 Real-World Example:
In 2015, the Apache Commons Collections vulnerability allowed RCE via unsafe deserialization in popular Java applications like Jenkins.

Prevention:
Avoid Java native serialization. Use formats like JSON or XML.
Use whitelisting to allow only known classes.
Implement integrity checks (e.g., digital signatures)
java
CopyEdit
// Avoid:
ObjectInputStream in = new ObjectInputStream(socket.getInputStream());
Object obj = in.readObject(); // Dangerous

// Use safer deserialization or validation frameworks instead

 
6. Sensitive Data Exposure
Developers often inadvertently expose sensitive data—through logs, debug statements, or lack of encryption.

🔍 How it Works:
Sensitive fields such as API keys, PII, or credit card data may be stored unencrypted or transmitted over unsecured channels.

💣 Real-World Example:
Equifax’s 2017 breach exposed Social Security numbers and other sensitive information for over 140 million people, partly due to insecure handling and delayed patching.

 Prevention:
Enforce HTTPS/TLS everywhere
Encrypt data at rest with AES-256
Redact secrets from logs
Use Vaults or environment variables to store secrets
 
7. Security Misconfiguration
This category includes open S3 buckets, exposed admin panels, verbose error messages, and default credentials.

🔍 How it Works:
Developers might leave services running in development mode or forget to disable debug endpoints.

💣 Real-World Example:
In 2020, hundreds of US-based websites leaked sensitive data due to misconfigured Elasticsearch servers exposed to the internet.

 Prevention:
Harden server configurations
Disable unused services and ports
Automate security checks with tools like Docker Bench or OpenSCAP
Avoid using admin/admin as default credentials
 
8. Unvalidated Redirects and Forwards
If redirect targets are determined by user input without validation, attackers can trick users into phishing pages.

🔍 How it Works:
An attacker crafts a link like:

pgsql
https://trusted.com/login?redirect=https://phishing.com

💣 Real-World Example:
Several high-profile phishing campaigns impersonated Google and Microsoft by abusing redirect logic on legitimate domains.

Prevention:
Validate redirect targets against an allowlist
Avoid including full URLs in parameters
Don’t use redirects for sensitive workflows like login
 
9. Using Components with Known Vulnerabilities
Your code is only as secure as your dependencies. Vulnerable open-source libraries introduce risk, even if your code is clean.

🔍 How it Works:
A widely used component, like Log4j, has a critical vulnerability. Attackers exploit it across any application using that version.

💣 Real-World Example:
The Log4Shell vulnerability in Log4j (2021) allowed RCE through simple log statements, affecting millions of Java applications.

Prevention:
Use tools like OWASP Dependency-Check, Snyk, or GitHub’s Dependabot
Monitor CVE databases
Automate patch management via CI/CD
 
10. Improper Access Control
Improper enforcement of authorization logic allows unauthorized access to resources and actions.

🔍 How it Works:
If endpoints trust role or permission claims from the client or don’t check session identity thoroughly, users may escalate privileges.

💣 Real-World Example:
Facebook and Instagram have both faced vulnerabilities where users could access private content due to broken access control on APIs.

Prevention:
Enforce access control at server-side layers
Implement Role-Based Access Control (RBAC)
Deny by default, and explicitly allow by role or permission
Use libraries like Spring Security or Keycloak to centralize access logic
 
Embedding Security into Development (Shift Left)
Security should not be an afterthought. By integrating security early into the Software Development Lifecycle (SDLC), teams reduce cost, risk, and complexity.

🛠 Tools to Integrate:
Static Application Security Testing (SAST): SonarQube, Semgrep
Dynamic Application Security Testing (DAST): OWASP ZAP, Burp Suite
Dependency Scanning: Snyk, OWASP Dependency-Check
Infrastructure Scanning: Trivy, Checkov, KICS
 
Final Thoughts
Secure code is not just about writing less bugs it’s about defending your users, your infrastructure, and your reputation. The cost of ignoring security is far greater than the cost of implementing best practices early.

Whether you’re modernizing a legacy Java application, building microservices in the cloud, or deploying AI agents, make security a cornerstone of your architecture.

At Cognexa, we help teams embed security from the codebase to the cloud. From vulnerability detection to AI-powered secure modernization, we believe in building the future—securely.