Top Mistakes Developers Make That Cause PCI Compliance Failures

The pressure on developers to quickly ship features while remaining compliant with PCI DSS and coding practices can often be overwhelming. This usually results in a series of compliance failures during audits and can widen the gap between delivering features on time and maintaining appropriate security standards.

With the PCI DSS 4.0 compliance requirements becoming fully mandatory on  March 31, 2025, it is imperative that developers become familiar with them. It is especially crucial that they understand the top mistakes that can lead to PCI compliance failures. A good grasp of these compliance failures can significantly reduce the costs of avoidable mistakes and help you avoid fines and sanctions.

Why Do Developer Mistakes Lead to PCI Compliance Failures?

The importance of secure coding training cannot be overstated, and developer errors can expose cardholder data, breaching PCI compliance requirements.

The truth is, a lack of secure coding knowledge can harm developers working on payment systems. When this is combined with urgent demands, security is often relegated to the sidelines.

What Are the PCI DSS 4.0 Requirements for Developers?

With the rollout of PCI DSS 4.0 Requirements 6.2.2 through 6.2.4, expectations for developing software that processes data have changed.  Requirement 6.2.4 specifically mandates that developers receive annual, practical secure coding training covering injection flaws, authentication and access control weaknesses, cryptographic failures, business logic errors, and other standard attack classes.

Requirement 6.2.2 focuses on establishing secure coding practices throughout the software development lifecycle, while Requirement 6.2.3 addresses code reviews before release. Together, these requirements create a framework where security must be considered at every stage of development, not bolted on at the end.

What Are the Most Common Developer Mistakes That Cause PCI Failures?

There are a couple of common developer mistakes that can cause PCI failures, including weak authentication and storing sensitive data. Here are some of the most common mistakes.

Developers Skip Secure Coding Training

Developers often skip secure coding training because they believe they lack the time, especially with sprint deadlines and pressure from their product managers. There is also the problem of boring, forgettable training videos and quizzes that check training boxes without substance.

Skipping secure coding training has begun to backfire in PCI audits. Nowadays, auditors look for evidence that developers have practiced the skills they learned in training, not just that they have completed courses covering various attack types. Checkbox-style training is no longer sufficient; hands-on, secure coding programs that detect and help developers fix vulnerabilities are essential now more than ever.

Weak Authentication Implementations Fail Audits

Weak authentication implementations fail PCI DSS audits when they violate PCI DSS requirements. This is particularly true for requirements that pertain to safeguarding access to cardholder data environments. Some common mistakes include not using multi-factor authentication (MFA) for administrator access, using weak password policies that don't meet complexity requirements, and storing hard-coded credentials in the application code.

Storing Sensitive Authentication Data Can Cause Failures

PCI DSS explicitly excludes retaining or storing certain data elements after a transaction is authorized. This sort of data includes complete track data from magnetic stripes, card verification codes (CVV2/CVC2), and PINs or PIN blocks. Even if this data is encrypted, storing it violates PCI requirements.

Injection Vulnerabilities Cause Compliance Issues

Several injection vulnerabilities can cause compliance issues, including SQL injection, LDAP injection, and command injection, among others. They create problems by making it easier for attackers to obtain direct access to cardholder data.  

PCI DSS 4.0 requires organizations  to implement secure coding practices that prevent injection flaws, and auditors must test for such gaps in security assessments.

Errors Can Occur Within Security and Compliance Guidelines

When developers faithfully follow security and compliance guidelines, they can still fall into traps or errors, including misconfiguring security controls, misunderstanding requirements, and inconsistently applying security measures across the application. Business logic errors, where code functions as designed but has inherent security weaknesses, fall into this category.  

What Are Three Top Challenges of PCI Compliance That an Organization Can Have?

There are three main challenges that many organizations face when trying to be PCI compliant.

How Do Poor Code Review Practices Lead to Failures?

Poor code review practices are a key challenge many organizations face when trying to be PCI compliant. This challenge can be particularly damaging because developers and the entire team assume that a proper code review has been conducted; meanwhile, many gaps and vulnerabilities will go unchecked into production. This problem often occurs when there aren't enough security experts on each development team.

Why Do Organizations Fail To Conduct Regular Security Assessments?

Organizations fail to conduct regular security assessments primarily due to resource constraints and competing priorities. Organizations need a stable budget to cover quarterly vulnerability scans and annual penetration tests.

Regular security testing, such as quarterly vulnerability assessments of systems under scope and yearly penetration testing, is mandated by the PCI DSS. When auditors verify their security posture, organizations that neglect or only partially complete these examinations will undoubtedly experience compliance problems.

How Do Third-Party Service Providers Impact Your Compliance?

Third-party service providers can affect compliance by providing external services, such as hosting or other functions, which often directly or indirectly affect data collection and storage. If these third parties experience a security breach, it could expose your customers’ payment data and put your company or team at risk of compliance consequences.

How Can Developers Prevent PCI Compliance Failures?

Two key ways developers can prevent PCI compliance failures are through proper training that meets PCI DSS requirements and by inculcating secure coding practices into their software development cycle.

What Type of Training Meets PCI DSS Requirements?

The type of training that complies with PCI DSS requirements must provide proof of work. It must be hands-on and comprehensive, identifying various attack types outlined in  Requirement 6.2.4. Developers have to work with actual code vulnerabilities, not just take multiple-choice questions and watch videos.

Security Journey’s approach to PCI compliance identifies this gap and provides a comprehensive, hands-on experience that helps developers identify and remediate errors and vulnerabilities. Developer Security Knowledge Assessments benchmark skills and track improvement over time, giving you evidence for auditors that training is actually building security competence. Monthly content updates ensure that training includes the latest threats, and companies can track progress and keep the necessary documents for certified security assessors with SCORM support for LMS connection.  

How Do You Implement Secure Coding Practices in Your Software Development Lifecycle?

The best way to implement secure coding practices in your software development lifecycle is to ensure that there are regular checks at every stage of development. You will have to include security activities in your workflow, such as testing and running code reviews, before moving on to the next stage. Take advantage of automated security testing tools that can easily identify obvious vulnerabilities before code reaches staging environments.

Training You Can Count On

Meeting PCI DSS 4.0 requirements doesn't mean you have to be constantly anxious about every audit. A thorough understanding of the common mistakes that contribute to compliance failures, along with proper secure code training and practices, can easily keep you compliant and secure.

For hands-on training that meets and exceeds PCI requirements, Security Journey’s lab and role-based learning paths provide developer-focused training systems to ensure developers are ready for on-field security challenges. We also provide human support, dedicated customer success managers, and the Security Champion Passport program to build internal security advocates.  Contact us today to learn more.