XSS in Windsurf-Generated Apps
Windsurf generates entire application scaffolds from natural language instructions. Its Cascade AI agent writes components rapidly, but often introduces cross-site scripting vulnerabilities by rendering user input as raw HTML rather than escaped text.
Scan Your Windsurf AppHow It Happens
Windsurf's Cascade agent generates React, Vue, and Svelte components based on high-level prompts. When users describe features like "display user comments with formatting" or "render blog post content," Cascade reaches for raw HTML injection methods because they deliver the visual result fastest. In React projects, Windsurf frequently outputs dangerouslySetInnerHTML without any sanitization wrapper. In Vue projects, it uses v-html directives on user-controlled data. In Svelte, it generates {@html content} blocks. Each framework has its own unsafe rendering path, and Windsurf uses all of them. Windsurf also generates URL handling code that reflects query parameters into page content without encoding. Because Cascade builds multi-file applications in a single pass, the unsafe pattern can propagate across dozens of components before the developer reviews any of them.
Impact
XSS in a Windsurf-generated app lets attackers inject malicious scripts that run in other users' browsers. This enables session theft, keylogging, phishing overlays, and unauthorized actions performed as the victim. Windsurf apps built with Supabase or Firebase backends are particularly vulnerable because authentication tokens are stored in browser-accessible storage. An XSS exploit can extract these tokens and give the attacker persistent access to the victim's account even after the XSS vector is fixed. Because Windsurf generates production-ready applications that developers deploy quickly, XSS vulnerabilities often reach production within hours of being generated, before any security review takes place.
How to Detect
Search the Windsurf-generated codebase for framework-specific unsafe rendering: dangerouslySetInnerHTML (React), v-html (Vue), {@html} (Svelte), or [innerHTML] (Angular). Each instance is a potential XSS vector. Test every input field and URL parameter by injecting payloads like <img src=x onerror=alert(document.domain)>. Focus on search pages, profile displays, comment sections, and any component that shows user-generated content. Vibe App Scanner detects these patterns automatically by analyzing the deployed JavaScript bundle and testing reflected input vectors across every route Windsurf generated.
How to Fix
Install DOMPurify and create a project-level sanitization utility. Place it in a shared location so Cascade is more likely to reference it when generating new components. For React: always sanitize before dangerouslySetInnerHTML. For Vue: sanitize before v-html. For Svelte: sanitize before {@html}. Better yet, replace raw HTML rendering with safe alternatives. Use react-markdown for markdown content, or render user text as plain text nodes that frameworks auto-escape by default. Add a Content-Security-Policy header that disallows inline scripts (script-src 'self'). This blocks XSS execution even if a sanitization gap exists. Configure ESLint or your framework's linter to flag all unsafe rendering patterns. This catches new XSS vectors as Windsurf generates additional components.
Code Examples
Windsurf-generated blog post renderer
// Windsurf Cascade output
function BlogPost({ post }: { post: Post }) {
return (
<article>
<h1>{post.title}</h1>
<div dangerouslySetInnerHTML={{ __html: post.body }} />
</article>
)
}import DOMPurify from 'dompurify'
function BlogPost({ post }: { post: Post }) {
return (
<article>
<h1>{post.title}</h1>
<div
dangerouslySetInnerHTML={{
__html: DOMPurify.sanitize(post.body)
}}
/>
</article>
)
}Frequently Asked Questions
Does Windsurf's Cascade agent consider security when generating code?
Cascade prioritizes functionality and speed. It does not consistently apply security best practices like input sanitization. You should treat all Cascade-generated code that handles user input as potentially unsafe until reviewed.
Is Windsurf more vulnerable to XSS than other AI IDEs?
Windsurf generates multi-file applications in a single pass, which means unsafe patterns can spread across many components before review. The risk level is comparable to other AI code generators, but the blast radius per generation is larger.
Can I prompt Windsurf to generate secure code?
Including instructions like "always sanitize user input with DOMPurify" in your prompt helps, but is not reliable. The best approach is adding a .windsurfrules file with security guidelines and having a sanitization utility already in the project for Cascade to reference.
Related Security Resources
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