Top 10 Security Vulnerabilities Every Developer Should Know

Security work is thankless. When you do it well, nothing visible happens. No customer thanks you, no manager praises your work. But miss something? All hell breaks loose. Security is the only part of engineering where success is invisible and failure is a public execution.

With AI-generated code becoming the norm, security incidents will occur more often. If you want to stand out, understanding security fundamentals is a solid bet. The best place to start is OWASP's Top 10 security threats for 2025.

OWASP (Open Worldwide Application Security Project) is a non-profit that's been holding the internet together for over two decades. They maintain a catalog of weaknesses, testing guides, and cheat sheets that every developer should read—but most never do until they're already in trouble.

Let's break down the 2025 list and what you can actually do about each one.

1. Broken Access Control

Broken access control is the #1 security risk—again. It appeared in almost 4% of tested applications. Even Next.js had a bug months back where attackers could bypass authorization by setting a specific HTTP header.

Access control enforces that users can't act outside their intended permissions. User A shouldn't read User B's private data. More critically, User A shouldn't get admin roles if they're not authorized.

How to Prevent It:

Deny access by default. Unless something is explicitly public, block it. Don't scatter access rules across your app—implement security once and reuse it everywhere. Minimize CORS usage and configure it carefully. Invalidate session identifiers on logout, and keep JWT tokens short-lived. Most importantly, enforce record-level ownership. If User A requests User B's invoice, that should fail loudly.

@Service
public class InvoiceService {
    
    public Invoice getInvoice(Long invoiceId, Long userId) {
        Invoice invoice = invoiceRepository.findById(invoiceId)
            .orElseThrow(() -> new NotFoundException("Invoice not found"));
        
        // Enforce ownership - don't just check if invoice exists
        if (!invoice.getOwnerId().equals(userId)) {
            throw new ForbiddenException("Access denied to this invoice");
        }
        
        return invoice;
    }
}

2. Security Misconfiguration

Security misconfiguration happens when systems ship with insecure defaults, missing hardening, or wide-open permissions. Exposed admin panels, verbose error messages, cloud buckets you assumed were private but never verified—these all fall under this category.

I guarantee there's at least one S3 bucket somewhere that should be private but isn't.

How to Prevent It:

Treat your setup like production from day one. Automate a hardened baseline config across all environments, then loosen requirements for dev and test. Don't leave sample apps, debug tools, or unused services lying around. Check your cloud permissions—don't trust defaults. Audit your setup regularly.

# application-prod.yml
server:
  error:
    include-message: never
    include-stacktrace: never
    include-binding-errors: never
    
management:
  endpoints:
    web:
      exposure:
        include: health,metrics
  endpoint:
    health:
      show-details: never

3. Software Supply Chain Failures

This used to be about outdated dependencies. Now it covers the full chaos of modern software delivery—compromised packages, rogue maintainers, poisoned Docker images. It ranked #1 in the OWASP community survey, with 50% of respondents putting it at the top.

Remember the left-pad incident? That was cute. Now we have packages that start mining crypto or exfiltrate environment variables.

How to Prevent It:

Don't use shady packages from unknown sources. This applies to both coding and life in general. Pin your dependencies to specific versions. Use lockfiles. Scan dependencies for known vulnerabilities. For high-risk environments, host an internal package mirror with vetted packages so you're not relying on strangers' good behavior.

<!-- Pin specific versions in pom.xml -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <version>3.2.1</version> <!-- Explicit version, not 'LATEST' -->
</dependency>

4. Cryptographic Failures

You're vulnerable if you're still using MD5 or SHA1, rolling your own random number generators, or storing secrets in plain text. Extra points if you're committing private keys to source control.

How to Prevent It:

Don't commit passwords or keys to your repository. Use environment variables or secrets management tools. Encrypt sensitive data in transit using modern protocols. Hash passwords using adaptive algorithms like Argon2 or bcrypt—not MD5. Stop using outdated crypto libraries.

@Service
public class PasswordService {
    
    private final PasswordEncoder passwordEncoder;
    
    public PasswordService() {
        // Use bcrypt with strength 12 (2^12 iterations)
        this.passwordEncoder = new BCryptPasswordEncoder(12);
    }
    
    public String hashPassword(String rawPassword) {
        return passwordEncoder.encode(rawPassword);
    }
    
    public boolean verifyPassword(String rawPassword, String hashedPassword) {
        return passwordEncoder.matches(rawPassword, hashedPassword);
    }
}

5. Injection

Injection is probably the only vulnerability you remember from that one web security class before switching to frontend tutorials. It happens when untrusted input is fed into an interpreter without proper handling—SQL queries, shell commands, ORM filters, server-side templates. The system treats input as code instead of data.

If your user's first name is DROP DATABASE, you might be in trouble.

How to Prevent It:

Keep data and commands separate. Use parameterized queries, input sanitization, and escaping mechanisms. Modern frameworks give you these tools—actually use them.

And yes, prompt injection is now a thing. If you're feeding user input into an LLM wrapper without strict context management, you've recreated SQL injection—except this time it costs more, hallucinates confidently, and still leaks everything.

// Bad - string concatenation
String query = "SELECT * FROM users WHERE email = '" + email + "'";

// Good - parameterized query
@Query("SELECT u FROM User u WHERE u.email = :email")
User findByEmail(@Param("email") String email);

6. Insecure Design

This one is broader—it's about architectural decisions. Building a document preview feature without checking ownership. Implementing a backdoor for admin access that regular users can easily discover. These are design flaws, not implementation bugs.

A secure design can still have implementation defects, but an insecure design can't be fixed by perfect implementation.

How to Prevent It:

This requires experience and understanding of both your tools and your product. Think like a malicious user before writing a single line of code. Threat model your features. Ask "what if someone tries to abuse this?" before shipping.

7. Authentication Failures

Authentication failures occur when a system can't reliably verify who a user is. Attackers pretend to be someone they're not, and the system believes them. This includes brute-forceable login forms, broken session handling, and insecure "forgot password" flows.

How to Prevent It:

Enforce strong, long passwords. Block known common passwords from the start. Enable multi-factor authentication. Don't allow unlimited login attempts—rate limit authentication requests and introduce increasing delays.

Brute forcing passwords is easier than ever with leaked databases floating around and GPU farms rented for pennies.

@Service
public class AuthenticationService {
    
    private final RateLimiter loginRateLimiter;
    
    public AuthResult authenticate(String email, String password, String ipAddress) {
        // Rate limit by IP to prevent brute force
        if (!loginRateLimiter.tryAcquire(ipAddress)) {
            throw new TooManyRequestsException("Too many login attempts. Try again later.");
        }
        
        User user = userRepository.findByEmail(email)
            .orElseThrow(() -> {
                // Same delay for non-existent users to prevent enumeration
                simulatePasswordCheck();
                return new AuthenticationException("Invalid credentials");
            });
        
        if (user.isLocked()) {
            throw new AuthenticationException("Account locked. Contact support.");
        }
        
        if (!passwordEncoder.matches(password, user.getPasswordHash())) {
            user.incrementFailedAttempts();
            if (user.getFailedAttempts() >= MAX_FAILED_ATTEMPTS) {
                user.lock();
            }
            userRepository.save(user);
            throw new AuthenticationException("Invalid credentials");
        }
        
        user.resetFailedAttempts();
        return generateTokens(user);
    }
}

8. Software or Data Integrity Failures

Any time you treat unverified code or data as safe, you're inviting attackers in. Auto-updating without checking signatures, pulling artifacts from random URLs, allowing users to modify serialized objects, relying on functionality from domains you don't control—all these create attack surfaces.

How to Prevent It:

Treat integrity as non-negotiable. Use digital signatures to verify that code or data hasn't been tampered with. Only pull dependencies from trusted repositories. In higher-risk environments, host your own internal mirror with vetted packages.

9. Security Logging and Alerting Failures

The worst thing that can happen is your application getting exploited without you noticing. If you're not logging authentication attempts, permission changes, unexpected errors, or access to sensitive endpoints, you're missing the only breadcrumbs that could tell you something's wrong.

How to Prevent It:

Set up centralized, tamper-resistant logging from the start. Monitor critical flows. Alert on suspicious activity like multiple failed login attempts or users accessing data outside their normal scope.

@Aspect
@Component
public class SecurityAuditAspect {
    
    private static final Logger auditLog = LoggerFactory.getLogger("SECURITY_AUDIT");
    
    @AfterReturning("@annotation(Audited)")
    public void logSuccess(JoinPoint joinPoint) {
        auditLog.info("action={} user={} result=SUCCESS args={}",
            joinPoint.getSignature().getName(),
            SecurityContext.getCurrentUser(),
            sanitize(joinPoint.getArgs()));
    }
    
    @AfterThrowing(value = "@annotation(Audited)", throwing = "ex")
    public void logFailure(JoinPoint joinPoint, Exception ex) {
        auditLog.warn("action={} user={} result=FAILURE error={}",
            joinPoint.getSignature().getName(),
            SecurityContext.getCurrentUser(),
            ex.getMessage());
    }
}

10. Mishandling of Exceptional Conditions

This is a new category that came into existence in 2025. It focuses on improper error handling, logical errors, failing open, and corner case scenarios. Cloudflare brought the internet down recently because of improper error handling of a file that was larger than expected.

These conditions include null pointer dereferences, missing parameters, exposing stack traces in production, failing to check permissions before executing operations, or assuming every function will behave as expected under every condition.

How to Prevent It:

Assume failure will happen. Build for failure first. Monitor for repeated errors. If the same error shows up a thousand times in a minute, something is very wrong.

@RestControllerAdvice
public class GlobalExceptionHandler {
    
    private static final Logger log = LoggerFactory.getLogger(GlobalExceptionHandler.class);
    
    @ExceptionHandler(Exception.class)
    public ResponseEntity<ErrorResponse> handleUnexpected(Exception ex, HttpServletRequest request) {
        String errorId = UUID.randomUUID().toString();
        
        // Log full details for debugging
        log.error("Unexpected error [id={}] path={}", errorId, request.getRequestURI(), ex);
        
        // Return safe response - no stack trace, no internal details
        return ResponseEntity.status(500)
            .body(new ErrorResponse(
                "An unexpected error occurred",
                errorId,  // Reference ID for support
                Instant.now()
            ));
    }
    
    @ExceptionHandler(ValidationException.class)
    public ResponseEntity<ErrorResponse> handleValidation(ValidationException ex) {
        // Validation errors can include more details since they're expected
        return ResponseEntity.badRequest()
            .body(new ErrorResponse(ex.getMessage(), null, Instant.now()));
    }
}

Wrapping Up

Security isn't glamorous. When you do it well, nothing visible happens. But every item on this list has caused real incidents—data breaches, service outages, financial losses.

The good news is that most of these issues are preventable with good practices: validate input, encrypt sensitive data, log security events, handle errors gracefully, and never trust user input. These aren't revolutionary ideas, but they require discipline to apply consistently.

Start with the basics. Audit your current applications against this list. Fix the obvious issues first. Security is an ongoing practice, not a one-time task.

---

For more details on the OWASP Top 10, check the official OWASP Top 10:2025 documentation.

🔗 Blog 🔗 LinkedIn 🔗 Medium 🔗 Github