A recent SecureFlag study found that 74% of companies admitted to having insecure coding practices, leading to at least one security breach in the past year. Not only that, but almost half of those organizations had to deal with multiple incidents.
Most teams spend their time on back-end defenses, but attackers often take another route, directly from the front end, where users interact and data is entered. If that layer isn’t secure, everything behind it is at risk.
What is Front-End Security?
For those that need a refresh, front-end security protects the parts of an application that users see and interact with, such as HTML, CSS, JavaScript, and client-side storage. Since these components are directly exposed to users (and therefore attackers), they’re a typical entry point for malicious activity.
The goal of front-end security is to prevent vulnerabilities from becoming data breaches or unauthorized access, compromising user trust. Developers should actively defend against threats before they become a problem, not once code is already in production.
Why Front-End Security Is Vital
The front end is literally the face of the application and often its first (and sometimes only) line of defense. Every input field, script, and dependency represents a potential attack surface.
When the front end is compromised, attackers can steal credentials and manipulate how users interact with the site. That’s because the front end has direct access to user data, authentication tokens, and browser APIs.
Unfortunately, it only takes a single exploit in client-side code to damage both reputation and compliance efforts (no pressure, though!)
Front-end security is, of course, about protecting code, but it also extends to defending the user experience and safeguarding the entire application.
Front-End Security Risks
So what exactly do teams need to defend against? Here are the attacks every front-end developer needs to understand.
Cross-Site Scripting (XSS)
XSS remains a primary concern, featured in security frameworks such as the OWASP Top 10. It’s when an attacker manages to inject malicious scripts into a web page, which can then read cookies, capture keystrokes, or, in general, execute actions on the user’s behalf.
Last year, security researchers discovered XSS vulnerabilities in Hotjar that put over 1 million websites at risk of leaking OAuth credentials.
To prevent XSS, there needs to be proper output encoding, input validation, and the use of frameworks that automatically escape untrusted data.
Another good practice is to set a strong Content Security Policy (CSP) that can further restrict what scripts are allowed to run.
Cross-Site Request Forgery (CSRF)
CSRF has long been seen as a back-end vulnerability, but many of today’s most effective safeguards, such as same-site cookie restrictions, are enforced in the browser.
In a CSRF attack, a logged-in user is manipulated into making an unwanted request to a trusted site. This could result in unintended actions such as changing passwords or transferring funds.
Just recently, researchers uncovered a CSRF vulnerability in the newly released Atlas browser that allows attackers to inject malicious instructions, enabling hidden commands to execute silently.
The best defense is a combination of both front-end and back-end measures. Aside from same-site cookies, it should also include anti-CSRF tokens and validation of Origin and Referrer headers.
Insecure Client-Side Storage
Storing sensitive information such as tokens or credentials in LocalStorage, SessionStorage, or cookies without proper protection can expose users to attacks.
If an XSS vulnerability exists, attackers can read these values directly. Store only what is necessary in the browser, and use secure cookies or encrypted storage where possible.
Insecure Dependencies
Front-end projects rely heavily on third-party libraries and frameworks, and attackers sometimes compromise these packages or publish malicious lookalikes.
For example, earlier this year, a massive npm supply chain attack compromised hundreds of widely used packages with a combined total of billions of weekly downloads.
Always verify the source of dependencies, keep them updated, and use automated tools to identify known vulnerabilities.
Clickjacking
Clickjacking tricks users into clicking on hidden or disguised elements within a web page. Setting the appropriate frame-busting headers prevents your site from being embedded in untrusted pages.
However, what’s concerning is that researchers have found a new variant of this vulnerability called “DoubleClickjacking,” which uses a double-click sequence to cause clickjacking attacks and account takeovers.
Unfortunately, it bypasses traditional security methods, so developers can implement protective scripts that disable critical buttons until users show intentional actions, such as mouse movements or keyboard inputs.
Bypassable Client-Side Logic
Client-side JavaScript and DOM elements are visible in the browser, meaning attackers can modify or manipulate how the front end behaves. Any logic or rules enforced only in the browser can be bypassed, so no client-side data should be trusted. All critical validations, business rules, and security checks must be enforced on the server to ensure attackers cannot exploit these weaknesses.
Secure Frameworks and Libraries
Of course, JavaScript frameworks also have to be included when talking about security, such as React, Angular, and Vue.js.
When used correctly, they provide built-in safeguards. For example, React automatically escapes rendered content, Angular enforces strict contextual escaping, and Vue.js warns developers about potentially unsafe bindings.
Despite this, developers should stay up to date on security releases, avoid using outdated versions, and review third-party extensions or plugins before adding them.
Using a framework responsibly also means understanding its limitations. For instance, no framework can protect against logic flaws, weak authentication, or insecure configuration, as the developer must address those.
The Low-Code/No-Code Risk
Last year, it was estimated that 87% of enterprise developers use low-code development platforms for at least some of their development work. Both low-code and no-code platforms make it easier to build applications by offering visual interfaces with drag-and-drop functionality, and all teams need to do is combine pre-built components.
However, there are security issues when users working on these platforms haven’t received any training on security risks or what to look out for. When this happens, many vulnerabilities can arise and be damaging to organizations. OWASP even provides a Top 10 list of these security risks and how to prevent them.
AI and New Front-End Security Challenges
Most of us have probably experimented with (or are actively using) tools like GitHub Copilot and ChatGPT, which can produce functional code in seconds. The catch is that AI focuses on producing code that works, rather than code that is secure.
A study from earlier this year found that nearly half of AI-generated code contains security flaws, even though it appears ready for production. These security issues are often subtle because the code looks right at a glance.
With vibe coding, developers can use plain language to describe the functionality they need, and the AI generates code. It speeds things up, but once again, it comes with many security challenges. As more coding gets done by AI, new vulnerabilities start to find their way in.
How Teams Can Stay Secure
-
Review all AI-generated code carefully: Don’t trust the code just because it works. Check for subtle vulnerabilities like XSS, unsafe logic, or exposed data.
-
Test critical flows manually: Authentication, authorization, and sensitive interactions need extra attention, as AI can produce code that looks fine but hides risks.
-
Document assumptions and decisions: Keep the team aware of what AI-generated code is doing and where it might fail.
-
Train developers on AI risks: Understanding how AI can introduce security flaws and learning to code securely helps teams catch problems before they reach production.
Practical Front-End Security Tips
We get that security can feel overwhelming, especially with AI, supply chain attacks, and changing threats. However, many of these risks are preventable with some basic secure coding practices.
1. Validate Input on Both Sides
Client-side validation makes forms more user-friendly, but don’t rely on them alone. Always validate again on the server, as attackers can easily bypass front-end checks.
2. Use HTTPS
Make sure to serve content over HTTPS to protect data in transit. Mixed content (where some assets are loaded insecurely) should be removed to prevent interception or tampering.
3. Protect Sensitive Data
To safeguard data, don’t embed API keys or tokens directly in the client-side code. Rather, keep them on the server or behind a secure proxy.
4. Set Secure Headers
HTTP headers such as Strict-Transport-Security, X-Content-Type-Options, Referrer-Policy, and CSP can help harden applications against some attacks.
5. Test and Monitor Regularly
Integrate security checks into your CI/CD pipeline. Static analysis, dependency scanners, and penetration tests can catch problems early, before they reach production.
6. Train Continuously
Developers who understand how vulnerabilities work can prevent mistakes before they happen, and ongoing training keeps the team prepared.
How SecureFlag Helps Build Safer Front-End Applications
Front-end vulnerabilities can be subtle and easily overlooked during development. SecureFlag helps developers build the skills to recognize and prevent these issues through practical, hands-on training.
SecureFlag’s labs replicate real-world attack scenarios and guide developers through identifying and fixing the underlying vulnerabilities.
In addition to the labs, SecureFlag also offers learning paths for front-end secure coding with Angular, React, and Vue.js. These structured programs guide developers through the essential security principles of each framework step by step.
When training is fun and engaging, teams can develop safer software while helping secure the organization.
