diff --git a/CHANGELOG.md b/CHANGELOG.md
index fde4901241..7e25ef3355 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,8 +15,8 @@
 - Fix: デッキのタイムラインカラムで「センシティブなファイルを含むノートを表示」設定が使用できなかった問題を修正
 
 ### Server
--
-
+- Fix: Nested proxy requestsを検出した際にブロックするように
+  [ghsa-gq5q-c77c-v236](https://github.com/misskey-dev/misskey/security/advisories/ghsa-gq5q-c77c-v236)
 
 ## 2024.10.1
 
diff --git a/packages/backend/src/server/FileServerService.ts b/packages/backend/src/server/FileServerService.ts
index 41b6d2e83d..bf0a011699 100644
--- a/packages/backend/src/server/FileServerService.ts
+++ b/packages/backend/src/server/FileServerService.ts
@@ -319,6 +319,12 @@ export class FileServerService {
 			);
 		}
 
+		if (!request.headers['user-agent']) {
+			throw new StatusError('User-Agent is required', 400, 'User-Agent is required');
+		} else if (request.headers['user-agent'].toLowerCase().indexOf('misskey/') !== -1) {
+			throw new StatusError('Refusing to proxy a request from another proxy', 403, 'Proxy is recursive');
+		}
+
 		// Create temp file
 		const file = await this.getStreamAndTypeFromUrl(url);
 		if (file === '404') {