In today’s interconnected world, organizations are increasingly reliant on web applications to support business-critical operations. Academic, financial, healthcare, and government platforms have benefited from the convenience and functionality that these services bring. But this convenience has created a target-rich environment for cybercriminals to exploit. Because of this, the cost of a breach has never been higher, both financially and reputationally.
According to IBM’s 2024 Cost of a Data Breach Report, the global average cost of a data breach reached $4.88 million, an increase of almost half a million dollars from the previous year. Looking specifically at data breaches involving data stored in public clouds, the average cost of a breach is even higher at $5.17 million. Beyond the financial toll, a data breach can have a sizable impact on customer trust, which is hard-won and easily lost.
In 2024, a high-profile health provider suffered a breach that cost the organization between $2.3 – $2.45 billion in losses due to incident response and remediation, regulatory fines, and legal fees. The culprit? A lack of multi-factor authentication on publicly-facing systems, leading to the compromise of internal systems and widespread ransomware.
Additionally, in early 2025, a major retail chain suffered a breach due to a vulnerable third-party JavaScript library, exposing the personal and payment information of millions of customers.
These security incidents highlight that web applications are only as secure as their weakest point, and that attackers will not hold back from identifying and exploiting them.
In this article, we’re going to look at the two main domains of common web application security attacks: server-side attacks and client-side attacks. Additionally, we’ll look at technical and procedural defenses that can help prevent these attacks, and the different kinds of security assessments and training that can help ensure these defenses are working properly.
To start, let’s look at our two main attack domains and the types of application vulnerabilities that an attacker will attempt to exploit.
Attack Domains
Attack domains are the vectors used by attackers to exploit vulnerabilities, including server-side attacks that target backend systems like databases and application servers, and client-side attacks that attempt to compromise the user’s browser and device. Understanding both types is crucial for building comprehensive security strategies for your web applications.
Server-Side Attacks
Server-side attacks target the server or backend infrastructure of a web application. These attacks attempt to exploit these back-end services to install malicious software, extract sensitive data, and bypass security controls. Common types of server-side attack vectors from the OWASP Top 10 include:
- SQL Injection (SQLi): A type of attack used by threat actors where malicious SQL code is inserted into a query via input fields or URL parameters, allowing attackers to access or manipulate the database.
- Remote Code Execution (RCE): When an attacker exploits a vulnerability to run malicious code on the server. This can be accomplished through methods such as malicious file uploads, deserialization attacks, buffer overflows, and abuse of user inputs.
- Insecure Direct Object References (IDOR): When attackers abuse user-controlled parameter values to gain direct access to data objects without properly validating a user’s authorization.
- Authentication Attacks: Exploiting weaknesses, including broken access controls, against credential management systems due to weak passwords, password reuse/credential stuffing, MFA bypass, or credential forgery.
- Server-Side Request Forgery (SSRF): Where attackers manipulate the server into sending unintended and malicious requests, potentially compromising internal systems or data.
Client-Side Attacks
Client-side attacks exploit the user’s browser, often by injecting malicious scripts into the web pages they visit. These are especially dangerous because they directly affect the user experience and are harder to detect from the server side. Common types of client-side attack techniques include:
- Clickjacking: A type of attack where a legitimate website is loaded into a malicious frame controlled by the attacker, tricking users into clicking on hidden objects in the page that deliver sensitive information to the attacker without any indication that the user has been compromised. This allows malicious actors to perform unauthorized actions through the authenticated user.
- Cross-Site Request Forgery (CSRF): An attack that forces an end user to perform unwanted actions on a web application that they are currently logged into. An example would be while authenticated to your banking site, a malicious site opens in another browser and uses your session to submit an unauthorized request to your bank, such as a money transfer or password change.
- Session Replay: When an attacker is able to obtain an authenticated session token that is not secured, they are able to reuse that token to login to the application as the compromised user.
- Third-Party Script Attacks: Application vulnerabilities introduced through external libraries or services embedded in the website which can contain malicious code.
- Injection Attacks: When an attacker is able to inject malicious scripts into webpages, user inputs, or forms that execute in the user’s browser, potentially stealing session tokens, credentials, or hijacking payment form data.
- Open Redirects: Application security vulnerabilities where a web application allows attackers to redirect users to an external URL without properly validating the destination, tricking users into visiting malicious sites.
Whether an attack is server-side or client-side, the ultimate impact is the same: loss of sensitive information and data, unauthorized access, and potential financial harm to the organization. While the attack vector may differ, the consequences to the organization may be substantial.
Thankfully, a number of the controls that are able to minimize these security risks overlap between both attack domains and will be discussed next.
Security Controls and Solutions
When it comes to web application security, we’re going to break these controls down into two separate groups: technical and administrative. Technical controls are software or hardware-based solutions that are used to protect systems and data. Administrative controls deal with policy, processes, and procedures that focus on the human element of security.
Technical Security Controls
Technical controls are mechanisms that enforce security policies using tools, configurations, and systems that are proactive in preventing successful attacks. There are many controls that can be implemented, but here we’ll briefly discuss some methods that help prevent the types of attacks discussed above:
- Firewalls, Intrusion Detection (IDS), and Prevention Systems (IPS): IDS, IPS, and Firewalls are the first lines of defense against network-based attacks. Used at the network boundary, they can limit the size of the exposed attack surface by only allowing traffic from approved networks (whitelisting) and denying traffic from untrusted networks on the internet (blacklisting). Additionally, they can be used to monitor for known attack patterns using Signature-Based and Heuristic monitoring and alert administrators, or deny traffic when there is a match.
- Strong Encryption: Strong Encryption protects web applications against cryptographic failure by securing data in transit to prevent malicious actors from intercepting or tampering with sensitive information such as login credentials, session IDs, or other sensitive data. It also ensures confidentiality and integrity at rest in databases and applications by encrypting stored data to prevent unauthorized exposure if the application is compromised.
- Strong Authentication Mechanisms: To protect sensitive user accounts, strong authentication mechanisms should require that the user has a strong password and that the system uses logging and monitoring to detect potential attacks. Some examples of this are having a minimum password length, requiring character complexity, and multi-factor authentication (MFA) on the user side. On the server/organization side, monitoring for brute-force attacks, implementing account lockout policies, alerting on failed login attempts, and routine password auditing to provide a strong security posture that is not solely reliant on the end user.
- Secure Coding Practices: To help prevent injection attacks, buffer overflows, open redirects, and other attacks that exploit the code used on the application, secure coding practices must be followed. By following well-established secure coding development guidelines, development teams reduce the risk of malicious actors exploiting application logic bugs or gaining unauthorized access to data and systems.
- Security Headers: Security headers protect web applications by instructing the browser to enforce specific security policies, such as blocking untrusted scripts, preventing clickjacking, and ensuring content is loaded securely over HTTPS. These headers reduce the browser’s exposure to common client-side attacks like cross-site scripting (XSS), cross-site request forgery (CSRF), and MIME type sniffing.
Administrative Security Controls
Administrative controls provide a foundation of policy, oversight, and governance to support technical controls. By keeping systems updated, logs monitored, and access tightly governed, organizations can significantly reduce the likelihood and impact of web application attacks. Here are some actionable steps to take:
- Patch and Change Management: To ensure that known and potential vulnerabilities in outdated software, frameworks, and libraries are quickly remediated, an efficient patch management program must be implemented to handle software updates. Organizations should implement a change management program that is also able to help prevent security misconfigurations or insecure code from being introduced into production by requiring testing, approval, and documentation before deployment.
- Log Monitoring and Incident Response: By logging web application activity, such as unauthorized access attempts, injection attacks, or session hijacking through centralized and monitored logs, suspicious activity can be discovered and responded to quickly and efficiently. A well-built incident response program additionally ensures timely analysis and remediation of security events, minimizing damage to the organization and protecting user credentials.
- Tamper Detection and Version Control: To ensure that any scripts running on an application are approved and authorized, tamper detection mechanisms like cryptographic hashes or digital signatures should be used to verify script integrity, while version control systems track changes and enforce the use of trusted, reviewed script versions.
- Access Controls and Governance: By ensuring that only authorized users can access specific systems, data, and functions, an organization can reduce the risk of privilege abuse, data exposure, and unauthorized changes. Governance practices avoid broken access controls by using role-based access control, separation of duties, and regular access reviews help maintain security integrity and accountability across the entire web application.
Additional Resources
In this discussion, we’ve explored the risks associated with web applications, including common attacks such as Structured Query Language injection (SQLi), remote code execution, and session replay. We covered the methods malicious actors use to exploit security vulnerabilities and detailed both technical and administrative controls, like secure coding, encryption, applying security patches, change management, and access controls, to defend against them.
In this final section, we’ll look at a few additional resources to further strengthen your understanding and implementation of web application security best practices.
Security Assessments
Security assessments help organizations proactively identify and remediate vulnerabilities before they can be exploited, reducing the risk of data breaches and service disruptions. They also support compliance with industry standards and regulations, enhance overall security maturity, and build confidence in the organization’s commitment to protecting its systems and data. Here are some best practices to implement for maximum impact:
- Auditing Security Controls and Procedures: Regular security audits of application security controls and procedures involve systematically evaluating an organization’s technical and administrative security measures to ensure they are properly implemented, effective, and aligned with internal policies and external compliance requirements.
- Verifying Compliance with Required Standards: Compliance standards provide a baseline for security by ensuring that established best practices and controls are consistently followed, reducing the likelihood of vulnerabilities and enhancing overall risk management.
- Continuing Education and Security Awareness Training: To ensure that developers and administrators stay informed about current threats, secure coding practices, and safe operational procedures, continuing education and security awareness training are crucial. This proactive approach helps prevent common types of vulnerabilities, such as SQLi or CSRF, from being introduced or exploited due to human error or outdated understanding of risks.
Penetration Testing
Penetration testing simulates real-world attacks to identify vulnerabilities that might be missed by automated tools, helping organizations understand how malicious actors could exploit weaknesses in their web applications. It provides actionable insights to strengthen defenses, validate existing security measures, and reduce the risk of breaches using dynamic application security testing.
- Identify Gaps in Security Controls: Penetration tests identify gaps in security controls by actively exploiting vulnerabilities to reveal weaknesses that may not be apparent through standard assessments, vulnerability scans, or configuration reviews.
- Risk Prioritization: Prioritizing vulnerabilities based on risk due to their exploitability and potential impact, rather than assigning them a calculated vulnerability score, enables organizations to allocate resources more effectively to address the most critical security issues.
- Technical Training: Penetration testing can be used as a tool to educate developers and administrators by providing them with verified vulnerabilities that help them to identify, understand, and mitigate real-world attacks.
Open-Source Resources
There are also several open-source resources available for developers, engineers, and administrators alike. Below is a list of a few of the highest-regarded industry standard guidelines:
- Open Worldwide Application Security Project (OWASP): In addition to the OWASP Top 10, there are a number of free, community-driven resources, tools, and best practices to help organizations improve the security of their web applications.
- SANS Institute: In addition to providing paid information security classes and certifications, the SANS Institute offers some free security policy templates aimed at helping administrators to build and maintain secure networks and applications:
- National Institute of Standards and Technology (NIST): NIST is a U.S. government agency that develops and promotes standards, guidelines, and best practices to enhance cybersecurity, including widely used frameworks for protecting information systems.
Final Thoughts
Web application attacks are ever-growing in frequency and sophistication, with real-world consequences for businesses and users alike. As attack surfaces expand through APIs, third-party integrations, and user-generated content, it’s more critical than ever to understand and address both server-side and client-side risks.
Cybersecurity is not just a technical issue — it’s a business imperative. Organizations must adopt a comprehensive, layered approach to security that protects not only their network and infrastructure but also their end users and applications. By empowering their security teams to do so, they avoid damage to their reputation, maintain customer trust, and prevent significant financial and operational losses.
CampusGuard and its security division, RedLens InfoSec, offer comprehensive IT Security and compliance assessments, penetration testing, and security awareness training to support your compliance efforts and strengthen your security posture.
This month, we also launched ScriptSafe™, a powerful web security monitoring and alerting solution that defends against all types of client-side security threats and helps your organization meet PCI DSS requirements 6.4.3 and 11.6.1.
Contact us to learn more about how CampusGuard and RedLens InfoSec can help you strengthen your organization’s security posture. You can also request a demo to see ScriptSafe in action!
