Skip to content

Add strict security headers to fetch-url endpoint #1993

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Nov 24, 2025
Merged

Add strict security headers to fetch-url endpoint #1993

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
17 changes: 12 additions & 5 deletions src/routes/api/fetch-url/+server.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,14 @@ import { isValidUrl } from "$lib/server/urlSafety";

const MAX_FILE_SIZE = 10 * 1024 * 1024; // 10MB
const FETCH_TIMEOUT = 30000; // 30 seconds
const SECURITY_HEADERS: HeadersInit = {
// Prevent any active content from executing if someone navigates directly to this endpoint.
"Content-Security-Policy":
"default-src 'none'; frame-ancestors 'none'; sandbox; script-src 'none'; img-src 'none'; style-src 'none'; connect-src 'none'; media-src 'none'; object-src 'none'; base-uri 'none'; form-action 'none'",
"X-Content-Type-Options": "nosniff",
"X-Frame-Options": "DENY",
"Referrer-Policy": "no-referrer",
};

export async function GET({ url }) {
const targetUrl = url.searchParams.get("url");
Expand Down Expand Up @@ -43,18 +51,17 @@ export async function GET({ url }) {
}

// Stream the response back
const contentType = response.headers.get("content-type") || "application/octet-stream";
// Always return as text/plain to prevent any HTML/JS execution
const contentType = "text/plain; charset=utf-8";
const contentDisposition = response.headers.get("content-disposition");

const headers: HeadersInit = {
"Content-Type": contentType,
"Cache-Control": "public, max-age=3600",
...(contentDisposition ? { "Content-Disposition": contentDisposition } : {}),
...SECURITY_HEADERS,
};

if (contentDisposition) {
headers["Content-Disposition"] = contentDisposition;
}

// Get the body as array buffer to check size
const arrayBuffer = await response.arrayBuffer();

Expand Down
Loading