Information about Frontend is scattered across the web, so I compiled this guide for reference.

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Why the Frontend Is a Critical Vulnerability You Can’t Ignore.

By 2025, client-side code is no longer just a UI layer. Modern frontend apps manage sessions, call APIs, handle sensitive data, and store authentication tokens. Whether you're

, Vue, Angular, or another stack, your frontend is part of the attack surface—and everything in the browser can be compromised.

We’re seeing rising threats like XSS attacks, session leaks, and insecure third-party SDKs—especially in fintech, healthcare, and marketplace platforms.

During our audits, we regularly find critical bugs in code that passes all CI checks but remains vulnerable due to ill-conceived architectural decisions, missing web security headers, or poorly configured security policies such as CORS and CSP.

Top 3 Frontend Risk Zones Every Product Should Audit

One of the most common issues is storing access tokens in

or accessible JavaScript cookies, which makes them vulnerable to XSS or malicious browser extensions.

when possible. This keeps tokens out of JavaScript and reduces the attack surface.

Correct implementation of silent refresh and logout flows

Any time user input is rendered into the DOM, there’s a risk of XSS—especially in React, Vue, or Angular projects using custom widgets, markdown editors, or visual WYSIWYG components.

Integration of XSS protection libraries: DOMPurify, sanitize-html, etc. Code review of raw HTML logic

Missing or Misconfigured Content Security Policy (CSP)

CSP is one of the most effective defenses against XSS and malicious script injection. But it’s often disabled or misconfigured due to conflicts with analytics or chat scripts.

Align policy with essential tools (chat, analytics, payments)

More Details

There are a few more points worth noting. First, browser compatibility varies across different browsers. Second, performance optimization is crucial when handling large amounts of data. Finally, key management is also an important consideration.

Feel free to ask questions in the comments - I'll reply as soon as possible.

Reference: Frontend Security in 2025: Protecting Client-Side Code in React, Vue & More