SvelteKit has Insufficient Cross-Site Request Forgery Protection

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: address security advisory CVE-2023-29003 by including `text/plain` and `PUT`/`PATCH`/`DELETE` requests in set of blocked cross-origin requests for CSRF protection

@@ -51,9 +51,12 @@ export async function respond(request, options, manifest, state) {
 
 	if (options.csrf_check_origin) {
 		const forbidden =
-			request.method === 'POST' &&
-			request.headers.get('origin') !== url.origin &&
-			is_form_content_type(request);
+			is_form_content_type(request) &&
+			(request.method === 'POST' ||
+				request.method === 'PUT' ||
+				request.method === 'PATCH' ||
+				request.method === 'DELETE') &&
+			request.headers.get('origin') !== url.origin;
 
 		if (forbidden) {
 			const csrf_error = error(403, `Cross-site ${request.method} form submissions are forbidden`);

@@ -68,5 +68,12 @@ export function is_content_type(request, ...types) {
  * @param {Request} request
  */
 export function is_form_content_type(request) {
-	return is_content_type(request, 'application/x-www-form-urlencoded', 'multipart/form-data');
+	// These content types must be protected against CSRF
+	// https://developer.mozilla.org/en-US/docs/Web/API/HTMLFormElement/enctype
+	return is_content_type(
+		request,
+		'application/x-www-form-urlencoded',
+		'multipart/form-data',
+		'text/plain'
+	);
 }

@@ -58,15 +58,27 @@ test.describe('Cookies', () => {
 
 test.describe('CSRF', () => {
 	test('Blocks requests with incorrect origin', async ({ baseURL }) => {
-		const res = await fetch(`${baseURL}/csrf`, {
-			method: 'POST',
-			headers: {
-				'content-type': 'application/x-www-form-urlencoded'
+		const content_types = [
+			'application/x-www-form-urlencoded',
+			'multipart/form-data',
+			'text/plain'
+		];
+		const methods = ['POST', 'PUT', 'PATCH', 'DELETE'];
+		for (const method of methods) {
+			for (const content_type of content_types) {
+				const res = await fetch(`${baseURL}/csrf`, {
+					method,
+					headers: {
+						'content-type': content_type
+					}
+				});
+				const message = `request method: ${method}, content-type: ${content_type}`;
+				expect(res.status, message).toBe(403);
+				expect(await res.text(), message).toBe(
+					`Cross-site ${method} form submissions are forbidden`
+				);
 			}
-		});
-
-		expect(res.status).toBe(403);
-		expect(await res.text()).toBe('Cross-site POST form submissions are forbidden');
+		}
 	});
 });
 

@@ -328,13 +328,13 @@ export interface KitConfig {
 		reportOnly?: CspDirectives;
 	};
 	/**
-	 * Protection against [cross-site request forgery](https://owasp.org/www-community/attacks/csrf) attacks.
+	 * Protection against [cross-site request forgery (CSRF)](https://owasp.org/www-community/attacks/csrf) attacks.
 	 */
 	csrf?: {
 		/**
-		 * Whether to check the incoming `origin` header for `POST` form submissions and verify that it matches the server's origin.
+		 * Whether to check the incoming `origin` header for `POST`, `PUT`, `PATCH`, or `DELETE` form submissions and verify that it matches the server's origin.
 		 *
-		 * To allow people to make `POST` form submissions to your app from other origins, you will need to disable this option. Be careful!
+		 * To allow people to make `POST`, `PUT`, `PATCH`, or `DELETE` requests with a `Content-Type` of `application/x-www-form-urlencoded`, `multipart/form-data`, or `text/plain` to your app from other origins, you will need to disable this option. Be careful!
 		 * @default true
 		 */
 		checkOrigin?: boolean;