Top 10 Web Application Security Best Practices

Secure coding is the practice of designing and writing code that adheres to security best practices, making it more resilient to attacks and exploits from malicious actors or malware. The most efficient and effective way to improve code security is to embed it into the development process, ensuring that security is baked into the application from the beginning, rather than added as an afterthought. Security misconfigurations or other errors can be caught early in the process, before attackers can exploit them in a live environment. Secure coding also enables more robust threat modeling and automation, required to enable proactive defenses and protect against zero-day threats. The OWASP Secure Coding Practices Checklist is a quick reference guide to help ensure code conforms to coding best practices.

APIs play a critical role in modern application architectures, enabling different software components, services, and systems to communicate and exchange data efficiently. APIs are foundational to microservices, cloud-native development, integration between platforms, and AI-powered environments. According to the 2025 F5 State of Application Strategy Report, 68% of organizations use APIs to manage app delivery and security, while 58% of organizations call API sprawl a significant pain point.

However, because of their ubiquity in modern digital ecosystems, APIs have increasingly become a target for attackers. By their nature, APIs expose critical business logic and sensitive information, such as user data and authentication credentials, and they facilitate and support digital experiences including online access and purchasing, banking and financial transactions, and login services.

The OWASP Top 10 API Security Risks was first published in 2019 to underscore the potential risks APIs face and to illustrate how these risks may be mitigated. Building on the OWASP API security insights, here are four key API security strategies that provide a holistic approach to protecting APIs.

•  Discovery. Identify, map, and document all APIs across your environment—including known, unknown, deprecated, and shadow APIs—to fully understand your API threat surface
• Monitoring. Maintain continuous visibility into API usage and behavior over time. Monitoring helps detect anomalies that could indicate potential attacks, misuse, or compromise.
• Detection: Use automated testing and runtime analysis to identify vulnerabilities early in pre-production and once pushed into production. APIs that are unmonitored and unprotected can expose organizations to serious risks.
• Protection: Implement real-time, in-line security controls such as web application firewalls (WAFs), rate limiting, sensitive data masking, and API-specific protection rules to enforce policy, mitigate malicious or unwanted activity (including automated threats), and prevent the exposure of sensitive data via APIs.

Effective monitoring and logging are essential for maintaining strong web app security. These best practices allow you to detect vulnerabilities and threats quickly, trace the actions of an attacker, and accelerate response and remediation, whether through code updates or by applying additional security controls.

Best practices for secure logging include protecting sensitive data: Ensure any sensitive data is either masked or excluded from logs entirely. Never log confidential information such as passwords, credit card numbers, or personally identifiable information (PII). Also, avoid revealing too much in error messages. Limit the detail in public-facing error messages to prevent exposing information that attackers could use to exploit vulnerabilities.

Develop a comprehensive incident response plan to ensure your organization can act swiftly and effectively when a security incident occurs. A well-prepared plan should include clearly defined roles and responsibilities for each member of the incident response team and a security risk classification framework to assess the scope, severity, and potential impact of an incident. Be sure to include a range of mitigation strategies tailored to different types of threats, with damage containment procedures to prevent further harm while the incident is addressed. Provide guidelines for internal communication, reporting, and post-incident actions, including lessons learned and updates to prevent future occurrences.

In addition to developing your organization's internal incident response plan and strategies, be aware that your security provider likely also offers incident response services. The F5 security incident response team (F5 SIRT) offers emergency incident response with all support contracts, with 24/7 response to threats by experienced security engineers, and comprehensive mitigation with both immediate and long-term protection plans.  

The principle of least privilege states that users, systems, applications, and processes should have only the minimum level of access necessary to perform a specific job or task and nothing more. Limiting access reduces the attack surface by limiting the number of access points that can be exploited and minimizes the risk of accidental data exposure or mishandling by users. When applied to processes or systems, such as APIs, least privilege ensures that each API, service, or user interacting with an API only has the minimum access necessary to perform its intended function, containing potential damage caused by a malicious attack to those systems. Least access privilege also supports regulatory compliance for frameworks such as the General Data Protection Regulation (GDPR), the Payment Card Industry Data Security Standard (PCI-DSS), and the Health Insurance Portability and Accountability Act (HIPAA), which often require strict access control policies for personal and sensitive data.

Outdated software is an easy target for hackers, as known vulnerabilities are often publicly documented and easily exploited. Security patches included in software updates address critical flaws and protect systems from emerging threats. Make sure to regularly check for updates and patches for all the components of a web application, including the web server, operating system, database, and third-party libraries and frameworks. Remove unused software to reduce the attack surface, and replace outdated or unsupported applications that no longer receive security updates.

Developing and following a web application security checklist is vital for maintaining a strong security posture. Organizations can either create their own checklist tailored to their specific environment or adopt an established resource, such as the OWASP Web Security Testing Guide, which provides comprehensive best practices and testing procedures.

The primary goals of security testing include verifying secure coding practices, identifying and correcting any security misconfigurations, and ensuring that authentication, authorization, and identity management mechanisms are properly implemented. Additional objectives are to test input validation rules, confirm the use of strong encryption, pressure test business logic to identify potential abuse scenarios, and thoroughly locate and secure all APIs to ensure they are properly protected.

As AI technologies become deeply embedded in modern digital experiences, it’s increasingly essential to define and develop a clear AI strategy as part of web application security best practices. This strategy should encompass both protecting AI-powered applications from emerging threats and leveraging AI and machine learning to enhance your overall security posture.

Generative AI applications, in particular, introduce unique security risks, such as information leakage, unintended or unpredictable behavior, and the potential for malicious code to be injected into training data. To mitigate these risks, organizations should apply standard application security principles—including secure coding, access control, and vulnerability testing—while also addressing AI-specific concerns. These include verifying the integrity of training-data supply chains, and implementing safeguards like prompt sanitization, input validation, and prompt filtering to defend against injection attacks.

AI can also play a powerful role in enhancing web application security. It enables organizations to detect threats faster and more accurately, identify and patch vulnerabilities proactively, and automate repetitive security tasks to improve IT and security operational efficiency.

As applications become more decentralized and attackers more sophisticated, it’s increasing critical to implement a complete web application and API protection (WAAP) solution for robust web app protection and to simplify security operations across complex application environments.

A WAAP solution integrates several core security capabilities for end-to-end application protection, including a WAF to safeguard against common web app exploits. It also includes comprehensive API security, including API discovery and monitoring, threat detection, and runtime protection. A WAAP also delivers DDoS mitigation across network and application layers (Layers 3, 4, and 7), and provides bot protection and management that detects, classifies, and blocks malicious automated traffic while allowing legitimate bots to operate without disruption.

Key benefits of a WAAP include centralized security policy management to enable consistent protection across all environments, regardless of deployment architecture or location, along with a unified set of security controls for both applications and APIs. A WAAP also delivers improved visibility and anomaly detection across the entire threat landscape, with detailed audit trails and event correlation to support regulatory compliance and incident response.

A complete WAAP solution simplifies security operations while enhancing protection across increasingly complex application ecosystems.