diff --git a/package-lock.json b/package-lock.json
index 669fb22..8f6ab62 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -19,6 +19,7 @@
         "bcrypt": "^6.0.0",
         "daisyui": "^5.7.50",
         "drizzle-orm": "^0.45.4",
+        "mime": "^4.1.2",
         "mysql2": "^3.24.6",
         "nanostores": "^1.5.5",
         "pino": "^10.4.0",
@@ -5576,6 +5577,21 @@
         "url": "https://github.com/sponsors/jonschlinkert"
       }
     },
+    "node_modules/mime": {
+      "version": "4.1.2",
+      "resolved": "https://registry.npmjs.org/mime/-/mime-4.1.2.tgz",
+      "integrity": "sha512-ikRzZ2RwbUVDyL9SsU0f2Phcmav4yq5r8faH5ZZKHtOZrMBLnrQOrj0uvqZ5R1uQnj+RO7Wcklw/lAf81mP9LQ==",
+      "funding": [
+        "https://github.com/sponsors/broofa"
+      ],
+      "license": "MIT",
+      "bin": {
+        "mime": "bin/cli.js"
+      },
+      "engines": {
+        "node": ">=16"
+      }
+    },
     "node_modules/mime-db": {
       "version": "1.54.0",
       "resolved": "https://registry.npmjs.org/mime-db/-/mime-db-1.54.0.tgz",
diff --git a/package.json b/package.json
index cd56ce8..d7cb8d1 100644
--- a/package.json
+++ b/package.json
@@ -22,6 +22,7 @@
     "bcrypt": "^6.0.0",
     "daisyui": "^5.7.50",
     "drizzle-orm": "^0.45.4",
+    "mime": "^4.1.2",
     "mysql2": "^3.24.6",
     "nanostores": "^1.5.5",
     "pino": "^10.4.0",
diff --git a/src/actions/report.ts b/src/actions/report.ts
index 4f89ed0..0b3f002 100644
--- a/src/actions/report.ts
+++ b/src/actions/report.ts
@@ -9,6 +9,7 @@ import crypto from 'node:crypto';
 import path from 'node:path';
 import { sendWebhook, WebhookAction } from '@util/webhook.ts';
 import { allowedImageTypes, allowedVideoTypes } from '@util/media.ts';
+import mime from 'mime/lite';
 
 export const report = {
   submitReport: defineAction({
@@ -26,14 +27,6 @@ export const report = {
         .nullable()
     }),
     handler: async (input) => {
-      const fileSize = input.files?.reduce((prev, curr) => prev + curr.size, 0);
-      if (fileSize && fileSize > MAX_UPLOAD_BYTES) {
-        throw new ActionError({
-          code: 'BAD_REQUEST',
-          message: 'Die Anhänge sind zu groß'
-        });
-      }
-
       const report = await db.getReportByUrlHash({ urlHash: input.urlHash });
       if (!report) {
         throw new ActionError({
@@ -54,13 +47,33 @@ export const report = {
         }
       }
 
-      if (!UPLOAD_PATH) {
+      if (input.files && !UPLOAD_PATH) {
         throw new ActionError({
           code: 'FORBIDDEN',
           message: 'Es dürfen keine Anhänge hochgeladen werden'
         });
       }
 
+      let totalFilesSize = 0;
+      for (const file of (input.files ?? [])) {
+        const realType = mime.getType(file.name);
+        if (realType != file.type) {
+          throw new ActionError({
+            code: 'NOT_ACCEPTABLE',
+            message: `Falscher Dateityp für '${file.name}': ${realType}`
+          });
+        }
+
+        totalFilesSize += file.size;
+      }
+
+      if (totalFilesSize > MAX_UPLOAD_BYTES) {
+        throw new ActionError({
+          code: 'BAD_REQUEST',
+          message: 'Die Anhänge sind zu groß'
+        });
+      }
+
       const filePaths = [] as string[];
       try {
         await db.transaction(async (tx) => {