diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7352db8fab..c7ee4b0388 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -46,6 +46,7 @@
 - Fix: 共有機能をサポートしていないブラウザの場合は共有ボタンを非表示にする #11305
 - Fix: 通知のグルーピング設定を変更してもリロードされるまで表示が変わらない問題を修正 #12470
 - Fix: 長い名前のチャンネルにおける投稿フォームの表示が崩れる問題を修正
+- Fix: セキュリティ向上のためAiScriptの`Mk:apiExternal`を無効化
 
 ### Server
 - Enhance: MFM `$[ruby ]` が他ソフトウェアと連合されるように
diff --git a/packages/frontend/src/os.ts b/packages/frontend/src/os.ts
index 8093335a28..8aed5797e1 100644
--- a/packages/frontend/src/os.ts
+++ b/packages/frontend/src/os.ts
@@ -5,8 +5,8 @@
 
 // TODO: なんでもかんでもos.tsに突っ込むのやめたいのでよしなに分割する
 
-import { pendingApiRequestsCount, api, apiExternal, apiGet } from '@/scripts/api.js';
-export { pendingApiRequestsCount, api, apiExternal, apiGet };
+import { pendingApiRequestsCount, api, apiGet } from '@/scripts/api.js';
+export { pendingApiRequestsCount, api, apiGet };
 import { Component, markRaw, Ref, ref, defineAsyncComponent } from 'vue';
 import { EventEmitter } from 'eventemitter3';
 import insertTextAtCursor from 'insert-text-at-cursor';
diff --git a/packages/frontend/src/scripts/aiscript/api.ts b/packages/frontend/src/scripts/aiscript/api.ts
index fb7ab924b7..038ae23109 100644
--- a/packages/frontend/src/scripts/aiscript/api.ts
+++ b/packages/frontend/src/scripts/aiscript/api.ts
@@ -50,6 +50,7 @@ export function createAiScriptEnv(opts) {
 				return values.ERROR('request_failed', utils.jsToVal(err));
 			});
 		}),
+		/* セキュリティ上の問題があるため無効化
 		'Mk:apiExternal': values.FN_NATIVE(async ([host, ep, param, token]) => {
 			utils.assertString(host);
 			utils.assertString(ep);
@@ -60,6 +61,7 @@ export function createAiScriptEnv(opts) {
 				return values.ERROR('request_failed', utils.jsToVal(err));
 			});
 		}),
+		*/
 		'Mk:save': values.FN_NATIVE(([key, value]) => {
 			utils.assertString(key);
 			miLocalStorage.setItem(`aiscript:${opts.storageKey}:${key.value}`, JSON.stringify(utils.valToJs(value)));
diff --git a/packages/frontend/src/scripts/api.ts b/packages/frontend/src/scripts/api.ts
index 0f54f779a6..8f3a163938 100644
--- a/packages/frontend/src/scripts/api.ts
+++ b/packages/frontend/src/scripts/api.ts
@@ -56,54 +56,6 @@ export function api<E extends keyof Misskey.Endpoints, P extends Misskey.Endpoin
 	return promise;
 }
 
-export function apiExternal<E extends keyof Misskey.Endpoints, P extends Misskey.Endpoints[E]['req']>(
-	hostUrl: string,
-	endpoint: E, data: P = {} as any,
-	token?: string | null | undefined,
-	signal?: AbortSignal,
-): Promise<Misskey.api.SwitchCaseResponseType<E, P>> {
-	if (!/^https?:\/\//.test(hostUrl)) throw new Error('invalid host name');
-	if (endpoint.includes('://')) throw new Error('invalid endpoint');
-	pendingApiRequestsCount.value++;
-
-	const onFinally = () => {
-		pendingApiRequestsCount.value--;
-	};
-
-	const promise = new Promise<Misskey.Endpoints[E]['res'] | void>((resolve, reject) => {
-		// Append a credential
-		(data as any).i = token;
-
-		const fullUrl = (hostUrl.slice(-1) === '/' ? hostUrl.slice(0, -1) : hostUrl)
-				+ '/api/' + (endpoint.slice(0, 1) === '/' ? endpoint.slice(1) : endpoint);
-		// Send request
-		window.fetch(fullUrl, {
-			method: 'POST',
-			body: JSON.stringify(data),
-			credentials: 'omit',
-			cache: 'no-cache',
-			headers: {
-				'Content-Type': 'application/json',
-			},
-			signal,
-		}).then(async (res) => {
-			const body = res.status === 204 ? null : await res.json();
-
-			if (res.status === 200) {
-				resolve(body);
-			} else if (res.status === 204) {
-				resolve();
-			} else {
-				reject(body.error);
-			}
-		}).catch(reject);
-	});
-
-	promise.then(onFinally, onFinally);
-
-	return promise;
-}
-
 // Implements Misskey.api.ApiClient.request
 export function apiGet<E extends keyof Misskey.Endpoints, P extends Misskey.Endpoints[E]['req']>(
 	endpoint: E,