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How to build secure frontends: best practices for front-end application Development

by : varshagupta Category : Website Date :
secure front end application development practices

Understanding common front-end vulnerabilities and attacks is vital for protecting sensitive data and maintaining secure web applications. Despite common misconceptions, front-end security is a crucial aspect of web development. This overview highlights the most prevalent front-end vulnerabilities and effective strategies to prevent them:

  1. Cross-Site Scripting (XSS): Allows attackers to inject malicious JavaScript into web applications, targeting input fields like search boxes or comment sections.
  2. Cross-Site Request Forgery (CSRF): Tricks users into performing unintended actions, such as transferring funds, by embedding malicious requests within legitimate web elements.
  3. Clickjacking: Manipulates users into clicking on hidden elements, leading to actions like downloading malware or visiting malicious websites.
  4. Usage of Components with Known Vulnerabilities: Exploits vulnerabilities in third-party libraries or frameworks, which can lead to data breaches or server takeovers.

To mitigate these threats, best practices include implementing input validation, adopting HTTPS, using content security policies, conducting regular security testing, and educating users about security awareness. Employing modern frameworks, managing third-party libraries, and continuously monitoring for vulnerabilities are also essential for maintaining robust front-end security.

Common Front-End Vulnerabilities and Attacks: What You Need to Know

Understanding the most common front-end vulnerabilities and attacks is crucial in today’s internet environment where the risks to valuable and sensitive data are greater than ever. Several myths about security often obscure the focus on front-end security.

VulnerabilityDescriptionHow it Works
Cross-Site Scripting (XSS)A vulnerability in web applications that allows cybercriminals to inject JavaScript code for malicious purposes.Attackers typically target pages common to all users, like a website’s homepage or comment sections. They need access to a form or input field to insert their malicious code, often found in search fields or comment sections.
Cross-Site Request Forgery (CSRF)A malicious website exploit where unauthorized commands are sent from a user the web application trusts.Successful CSRF attacks trick victims into executing state-changing requests without their consent, such as transferring funds or changing email addresses. Attackers use methods like specially crafted image tags, hidden forms, or JavaScript XMLHttpRequests.
Clickjacking (UI Redress Attack)A vulnerability affecting most internet browsers, allowing attackers to control a victim’s webcam and microphone.Attackers manipulate legitimate website elements, causing users to unknowingly interact with hidden malicious content. Users may click buttons, thinking they are harmless, but can unknowingly download malware or visit malicious web pages.
Usage of Components with Known VulnerabilitiesVulnerable components in web applications (e.g., framework libraries) that can be exploited, potentially by automated tools.Attackers can identify and exploit these components, broadening the threat beyond targeted attackers. Successful exploitation can lead to data loss or server takeover. Applications using such components weaken their defenses and become susceptible to various attacks.

Enhancing Web Security: Effective Strategies for Frontend Attack Prevention

Best practices to prevent front-end attacks involve measures such as input validation, content security policies, HTTPS adoption, security headers, regular updates, code reviews, access controls, error handling, user education, security testing, awareness training, incident response planning, monitoring, and careful consideration of third-party integrations. Following these practices helps safeguard user data and enhance overall web security.

Mitigating Cross-Site Scripting (XSS) Threats

XSS attacks pose a significant and hazardous threat, involving the injection of malicious code into web applications, which can execute harmful actions when accessed by users.

These attacks often exploit insufficient input and output sanitization in web applications, leading to various types of attacks, including:

  • Clickjacking Attacks: Substituting legitimate web page elements with deceptive ones, such as replacing checkout buttons with links to fake banking pages or legitimate download buttons with malware download links.
  • Geolocation Data Theft: Utilizing XSS attacks to inject JavaScript libraries that capture users’ IP addresses, geolocation, and personal information, which can be used for personalized scams and phishing attempts.
  • Cryptomining: Injected code from XSS attacks can initiate crypto mining on users’ devices, potentially causing slowdowns and overheating issues, especially when many users visit a web application daily.

Protecting against XSS attacks involves implementing robust input sanitization and proper input filtering in your web application. 

For example, restricting mobile numbers to digits only or disallowing special characters in names can significantly enhance security by preventing most injection attacks on your web application.

Dealing with Denial of Service (DoS) Attacks

Web applications frequently face DoS (Denial of Service) and DDoS (Distributed Denial of Service) attacks, which can be challenging to mitigate. These attacks involve a barrage of requests targeting your web application, often orchestrated using compromised systems.

DoS attacks, typically stemming from a single system or a limited number of systems, may be manageable by blocking the IP address of the originating system.

DDoS attacks, however, present a more formidable challenge. They involve hundreds or thousands of systems simultaneously launching numerous requests at your web application. This onslaught strains the system and leads to severe performance degradation.

To defend against these attacks, consider implementing rate-limiting measures within your web application. Services such as CloudFlare or Imperva, as well as hardware-based solutions, can effectively filter and thwart these attacks before they reach your web application, safeguarding its availability and performance.

Securing Against Cross-Site Request Forgery (CSRF) Attacks

CSRF attacks aim to deceive users into unintentionally initiating actions different from their intended actions. For instance, a user logged into their banking application might encounter a deceptive “Download” button. At the same time, browsing, and clicking it could unknowingly transfer funds from their bank account to an attacker.

To thwart CSRF attacks, employ a token-based approach. Generate a unique token, akin to a md5sum or sha256sum of random characters, with each page load. This token is then transmitted to forms via HTTP headers during form submission.

Enhancing Security with Content Security Policy (CSP)

Leveraging Content Security Policy (CSP) stands as an effective measure for preventing XSS (Cross-Site Scripting) attacks. It involves employing an HTTP flag that communicates trusted sources to your browser, which are then permitted to be included as iFrames within your web application.

Any source or URL not explicitly specified within the Content Security Policy flag is disregarded and won’t be allowed or rendered within an iFrame on your web application.

Enabling CSP within your HTTP headers proves to be a valuable approach for significantly mitigating XSS attacks. When combined with X-Frame-Options, it forms a robust defense mechanism against XSS attacks in general.

If the header token value is missing or doesn’t match the expected value, the action is blocked, ensuring the user’s safety and preventing unauthorized operations.

Enhancing Web Application Security Through Modern Frameworks

In many cases, web application front-ends are constructed using widely used frameworks, forming the foundation of the application’s user interface. Any security vulnerability present within this framework can potentially jeopardize the entire web application.

Employing modern and regularly maintained frameworks can significantly enhance the security of your web application. These frameworks often incorporate built-in authentication handlers and other security functionalities, streamlining the implementation of essential security practices required for your web application.

Assessing the Security of Third-Party Libraries in Use

Third-party libraries are prevalent in web development, providing efficiency and ease when adding new features to your web application. However, vulnerabilities within these third-party libraries can pose significant security risks to your web application.

For instance, many web applications rely on third-party libraries for tasks like billing and customer purchases. Any vulnerability within these billing libraries can trigger various security issues, including user data exposure or redirecting users to phishing sites aiming to capture their payment card details.

Monitoring and manually inspecting third-party libraries can be challenging, especially for larger web applications. Thankfully, online vulnerability scanners are available to simplify and automate this process. They continuously assess third-party libraries, promptly notifying you of any discovered vulnerabilities, and ensuring your web application remains secure.

Prioritizing Security from Project Inception

The development of web applications often spans months or even years, subject to fluctuating developer teams, budget adjustments, evolving ideas, and shifting project directions.

Throughout these dynamic changes, maintaining the security of your project remains paramount. Embracing a security-first mindset right from the project’s outset guarantees its resilience against any unforeseen shifts, as emphasized in our earlier interview, “Builders vs. Breakers: Bridging the Gap Between Software Development and InfoSec with Tanya Janca.

Minimizing iFrame Usage When Feasible

iFrames serves as a convenient tool for integrating or loading external pages/frames into your current view, streamlining the development process. However, their utilization frequently occurs without the proper implementation of X-Frame-Options, creating vulnerability to clickjacking attacks and potential breaches of your web application’s security.

iFrame-based attacks can enable various malicious actions, such as playing deceptive videos, displaying fraudulent forms that appear legitimate, and coercing users into downloading harmful content, ultimately degrading the overall user experience of your web application.

Implementing Feature Policy Restrictions

By default, your web application can access and request various features from the user’s device. While this unrestricted access may be convenient during development, it can pose a security risk if not properly controlled. Attackers can exploit your application to manipulate these unrestricted feature flags or policies, potentially tricking users into enabling certain features that appear to be legitimately offered by your web application.

To prevent such requests originating from your web application, it’s advisable to employ the Feature-Policy HTTP header. For instance, configuring the following Feature Policy will instruct users’ web browsers to deny the specified features, even if requested by your web application:

“Feature-Policy”: camera ‘none’; microphone ‘none’;

This proactive measure enhances the security of your web application by restricting the activation of potentially sensitive device features.

Verifying Subresource Integrity for CDN-Sourced Libraries

Another crucial security measure is to validate the integrity of libraries fetched from 3rd-party Content Delivery Networks (CDNs). Many web applications rely on these CDNs to accelerate page loading and improve overall performance. However, if these libraries are tampered with through Man-in-the-Middle (MITM) attacks or if the CDN itself is compromised, malicious code can infiltrate your web application on the user’s end, resulting in a subpar user experience.

For instance:


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In the provided example, the popular Bootstrap CSS library is loaded with an integrity parameter containing a checksum. Your browser can verify this checksum, ensuring that if the CDN is compromised or the CSS file is altered, the integrity check will fail, and the file will not render in the user’s browser.

While this may, at most, result in a poorly rendered page, it serves as a safeguard to protect your web application’s integrity and reputation, ultimately prioritizing user safety and security.

Strengthening Security through Input Validation and Sanitization

To bolster security, front-end developers should implement stringent input validation and sanitization techniques. These practices play a pivotal role in safeguarding against common vulnerabilities such as cross-site scripting (XSS) and SQL injection attacks. Validation of user inputs should be performed comprehensively on both the client and server sides to ensure their adherence to predetermined formats and their freedom from malicious scripts or code. Additionally, the sanitization of user inputs is of utmost importance, as it serves to eliminate potentially harmful content and fortify defenses against any attempts aimed at injecting malicious code.

Enhancing User Security through Authentication and Authorization:

It is of paramount importance to establish robust authentication measures in order to shield user accounts from unauthorized access. To achieve this, adhere to stringent password policies, mandate the use of multi-factor authentication (MFA), and employ secure methods for storing user credentials, such as hashing and salting techniques. Furthermore, it is essential to implement effective authorization mechanisms that strictly control users’ access to resources, thereby thwarting potential privilege escalation attacks.

Conducting a Thorough Evaluation of Your NPM Packages

In today’s development landscape, npm packages play a pivotal role in expediting app development by providing tried-and-tested solutions. Rather than reinventing the wheel, developers often turn to these readily available resources. However, it’s essential to acknowledge that these packages may harbor vulnerabilities, which is where npm audit becomes an invaluable tool.

When you employ the npm install command to add a package to your project, npm audit is automatically triggered. Moreover, you have the option to manually initiate npm audit for packages installed locally. This process enables you to conduct a comprehensive security assessment of the package, generating a detailed report that highlights any potential dependency vulnerabilities and offers suggested remedies.

Here’s how you can run npm audit on your packages:

On the command line, navigate to your package directory by typing cd path/to/your-package-name and hitting Enter.

Verify that your package includes both package.json and package-lock.json files.

Type npm audit and press Enter.

Examine the audit report carefully, and take the recommended actions or conduct further investigation if necessary.

🚨 A Word of Caution

While npm packages are often open-source and readily available, it’s crucial not to select a package solely based on its title. Relying solely on package titles can be misleading. Instead, consider important factors such as the package’s backing community, download count, and ongoing maintenance. Opting for a reputable package that has undergone rigorous scrutiny is far preferable to selecting a package with limited recognition or support. Occasionally, packages may even become discontinued, warranting careful consideration before use.

Managing Cross-Origin Resource Sharing (CORS) for Enhanced Security

To bolster the security of your application, it’s crucial to set up CORS headers on your server. These headers define which domains have permission to access your front-end resources. This proactive measure serves as a defense against potential Cross-Origin Request Forgery (CSRF) and Cross-Site Script Inclusion (XSSI) attacks, enhancing the overall safety of your web application.

Steer Clear of Embedding Sensitive Data

It’s essential to avoid embedding confidential details such as API keys or passwords directly into your front-end code. Instead, adopt practices such as utilizing environment variables or secure backend services to manage and safeguard such sensitive information. This approach enhances the overall security of your application by preventing the exposure of critical data in your codebase.

Prioritize Dependency Scanning for Enhanced Security

Make it a routine to conduct regular scans and updates for your frontend dependencies. This proactive approach is crucial for identifying and addressing security vulnerabilities promptly. You can leverage tools like npm audit or yarn audit to efficiently detect and resolve any issues that may arise, thus fortifying the security of your application.

Enhance Error Handling for Improved Security

To bolster security, it’s imperative to refrain from disclosing sensitive information within error messages. Customize your error-handling procedures to present user-friendly messages that do not inadvertently reveal confidential details. This proactive approach ensures that users receive informative yet secure feedback when errors occur.

Implement Rate Limiting for Enhanced Security

To bolster security, consider implementing rate-limiting mechanisms to restrict the number of requests a user can make within a specific time frame. This strategic measure serves as a protective barrier against potential brute force attacks, helping safeguard your system from malicious intrusion attempts.

Vetting Third-Party Integrations for Security

Before incorporating any third-party scripts or libraries into your front end, it is essential to conduct a comprehensive review and assessment. Ensure that these external components align with security best practices. This proactive approach helps mitigate potential security risks and safeguards the integrity of your application.

Strengthen Frontend Security with Security Headers

To enhance the security of your front end, consider implementing security headers such as Content Security Policy (CSP) and Strict-Transport-Security (HSTS). These headers provide additional layers of protection, fortifying your application against various security threats and vulnerabilities.

Deploy Dynamic Application Security Testing (DAST) Scanner

Dynamic Application Security Testing, or DAST for short, is a powerful tool for identifying vulnerabilities within web applications. This frontend security practice involves simulating attacks to uncover potential weaknesses. Importantly, it doesn’t require access to the application’s source code. However, it’s worth noting that DAST scanning can be a time-consuming process.

Integrating DAST into the Development Lifecycle

Experienced developers can seamlessly integrate a DAST scanner into the development lifecycle. By doing so, vulnerabilities can be detected and addressed at an early stage, reducing potential risks.

Benefits of Implementing DAST:

  • Mitigation of Cyber Threats:
  • By adopting this frontend practice, you can effectively mitigate various cyber threats, including:
  • Cross-site scripting
  • SQL injection
  • Configuration errors
  • Encryption issues

Make sure to incorporate the DAST scanner into your runtime environment to maximize its effectiveness in identifying and addressing these threats.


In today’s digital landscape, understanding common front-end vulnerabilities and attacks is vital for protecting sensitive data and maintaining secure web applications. Despite common misconceptions, front-end security is a crucial aspect of web development. 

The overview highlights prevalent front-end vulnerabilities such as Cross-Site Scripting (XSS), Cross-Site Request Forgery (CSRF), clickjacking, and the usage of components with known vulnerabilities. To mitigate these threats, best practices include input validation, adopting HTTPS, using content security policies, conducting regular security testing, and educating users about security awareness. 

Employing modern frameworks, managing third-party libraries, and continuously monitoring for vulnerabilities are also essential for maintaining robust front-end security. By implementing these strategies, developers can enhance web application security and protect users from a wide range of potential attacks.

About Varsha Gupta I am an SEO professional and writer at VOCSO Digital Agency. I love to learn and write about digital marketing terms like SEO, social media, and SEM.

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