diff --git a/src/endpoints/avatars.js b/src/endpoints/avatars.js
index 73b995ffb..f84527670 100644
--- a/src/endpoints/avatars.js
+++ b/src/endpoints/avatars.js
@@ -9,6 +9,7 @@ import { sync as writeFileAtomicSync } from 'write-file-atomic';
 import { jsonParser, urlencodedParser } from '../express-common.js';
 import { AVATAR_WIDTH, AVATAR_HEIGHT } from '../constants.js';
 import { getImages, tryParse } from '../util.js';
+import { getFileNameValidationFunction } from '../middleware/validateFileName.js';
 
 export const router = express.Router();
 
@@ -17,7 +18,7 @@ router.post('/get', jsonParser, function (request, response) {
     response.send(JSON.stringify(images));
 });
 
-router.post('/delete', jsonParser, function (request, response) {
+router.post('/delete', jsonParser, getFileNameValidationFunction('avatar'), function (request, response) {
     if (!request.body) return response.sendStatus(400);
 
     if (request.body.avatar !== sanitize(request.body.avatar)) {
diff --git a/src/endpoints/backgrounds.js b/src/endpoints/backgrounds.js
index 0638415e6..13705fa7a 100644
--- a/src/endpoints/backgrounds.js
+++ b/src/endpoints/backgrounds.js
@@ -7,6 +7,7 @@ import sanitize from 'sanitize-filename';
 import { jsonParser, urlencodedParser } from '../express-common.js';
 import { invalidateThumbnail } from './thumbnails.js';
 import { getImages } from '../util.js';
+import { getFileNameValidationFunction } from '../middleware/validateFileName.js';
 
 export const router = express.Router();
 
@@ -15,7 +16,7 @@ router.post('/all', jsonParser, function (request, response) {
     response.send(JSON.stringify(images));
 });
 
-router.post('/delete', jsonParser, function (request, response) {
+router.post('/delete', jsonParser, getFileNameValidationFunction('bg'), function (request, response) {
     if (!request.body) return response.sendStatus(400);
 
     if (request.body.bg !== sanitize(request.body.bg)) {
diff --git a/src/endpoints/characters.js b/src/endpoints/characters.js
index 2aa2cca10..c7a2a02d4 100644
--- a/src/endpoints/characters.js
+++ b/src/endpoints/characters.js
@@ -14,6 +14,7 @@ import jimp from 'jimp';
 
 import { AVATAR_WIDTH, AVATAR_HEIGHT } from '../constants.js';
 import { jsonParser, urlencodedParser } from '../express-common.js';
+import { default as validateAvatarUrlMiddleware, getFileNameValidationFunction } from '../middleware/validateFileName.js';
 import { deepMerge, humanizedISO8601DateTime, tryParse, extractFileFromZipBuffer, MemoryLimitedMap, getConfigValue } from '../util.js';
 import { TavernCardValidator } from '../validator/TavernCardValidator.js';
 import { parse, write } from '../character-card-parser.js';
@@ -756,7 +757,7 @@ router.post('/create', urlencodedParser, async function (request, response) {
     }
 });
 
-router.post('/rename', jsonParser, async function (request, response) {
+router.post('/rename', jsonParser, validateAvatarUrlMiddleware, async function (request, response) {
     if (!request.body.avatar_url || !request.body.new_name) {
         return response.sendStatus(400);
     }
@@ -803,7 +804,7 @@ router.post('/rename', jsonParser, async function (request, response) {
     }
 });
 
-router.post('/edit', urlencodedParser, async function (request, response) {
+router.post('/edit', urlencodedParser, validateAvatarUrlMiddleware, async function (request, response) {
     if (!request.body) {
         console.error('Error: no response body detected');
         response.status(400).send('Error: no response body detected');
@@ -852,7 +853,7 @@ router.post('/edit', urlencodedParser, async function (request, response) {
  * @param {Object} response - The HTTP response object.
  * @returns {void}
  */
-router.post('/edit-attribute', jsonParser, async function (request, response) {
+router.post('/edit-attribute', jsonParser, validateAvatarUrlMiddleware, async function (request, response) {
     console.log(request.body);
     if (!request.body) {
         console.error('Error: no response body detected');
@@ -898,7 +899,7 @@ router.post('/edit-attribute', jsonParser, async function (request, response) {
  *
  * @returns {void}
  * */
-router.post('/merge-attributes', jsonParser, async function (request, response) {
+router.post('/merge-attributes', jsonParser, getFileNameValidationFunction('avatar'), async function (request, response) {
     try {
         const update = request.body;
         const avatarPath = path.join(request.user.directories.characters, update.avatar);
@@ -929,7 +930,7 @@ router.post('/merge-attributes', jsonParser, async function (request, response)
     }
 });
 
-router.post('/delete', jsonParser, async function (request, response) {
+router.post('/delete', jsonParser, validateAvatarUrlMiddleware, async function (request, response) {
     if (!request.body || !request.body.avatar_url) {
         return response.sendStatus(400);
     }
@@ -992,7 +993,7 @@ router.post('/all', jsonParser, async function (request, response) {
     }
 });
 
-router.post('/get', jsonParser, async function (request, response) {
+router.post('/get', jsonParser, validateAvatarUrlMiddleware, async function (request, response) {
     try {
         if (!request.body) return response.sendStatus(400);
         const item = request.body.avatar_url;
@@ -1011,7 +1012,7 @@ router.post('/get', jsonParser, async function (request, response) {
     }
 });
 
-router.post('/chats', jsonParser, async function (request, response) {
+router.post('/chats', jsonParser, validateAvatarUrlMiddleware, async function (request, response) {
     if (!request.body) return response.sendStatus(400);
 
     const characterDirectory = (request.body.avatar_url).replace('.png', '');
@@ -1160,7 +1161,7 @@ router.post('/import', urlencodedParser, async function (request, response) {
     }
 });
 
-router.post('/duplicate', jsonParser, async function (request, response) {
+router.post('/duplicate', jsonParser, validateAvatarUrlMiddleware, async function (request, response) {
     try {
         if (!request.body.avatar_url) {
             console.log('avatar URL not found in request body');
@@ -1207,7 +1208,7 @@ router.post('/duplicate', jsonParser, async function (request, response) {
     }
 });
 
-router.post('/export', jsonParser, async function (request, response) {
+router.post('/export', jsonParser, validateAvatarUrlMiddleware, async function (request, response) {
     try {
         if (!request.body.format || !request.body.avatar_url) {
             return response.sendStatus(400);
diff --git a/src/endpoints/chats.js b/src/endpoints/chats.js
index 2df194797..c3bab87ac 100644
--- a/src/endpoints/chats.js
+++ b/src/endpoints/chats.js
@@ -9,6 +9,7 @@ import { sync as writeFileAtomicSync } from 'write-file-atomic';
 import _ from 'lodash';
 
 import { jsonParser, urlencodedParser } from '../express-common.js';
+import validateAvatarUrlMiddleware from '../middleware/validateFileName.js';
 import {
     getConfigValue,
     humanizedISO8601DateTime,
@@ -294,7 +295,7 @@ function importRisuChat(userName, characterName, jsonData) {
 
 export const router = express.Router();
 
-router.post('/save', jsonParser, function (request, response) {
+router.post('/save', jsonParser, validateAvatarUrlMiddleware, function (request, response) {
     try {
         const directoryName = String(request.body.avatar_url).replace('.png', '');
         const chatData = request.body.chat;
@@ -310,7 +311,7 @@ router.post('/save', jsonParser, function (request, response) {
     }
 });
 
-router.post('/get', jsonParser, function (request, response) {
+router.post('/get', jsonParser, validateAvatarUrlMiddleware, function (request, response) {
     try {
         const dirName = String(request.body.avatar_url).replace('.png', '');
         const directoryPath = path.join(request.user.directories.chats, dirName);
@@ -347,7 +348,7 @@ router.post('/get', jsonParser, function (request, response) {
 });
 
 
-router.post('/rename', jsonParser, async function (request, response) {
+router.post('/rename', jsonParser, validateAvatarUrlMiddleware, async function (request, response) {
     if (!request.body || !request.body.original_file || !request.body.renamed_file) {
         return response.sendStatus(400);
     }
@@ -372,7 +373,7 @@ router.post('/rename', jsonParser, async function (request, response) {
     return response.send({ ok: true, sanitizedFileName });
 });
 
-router.post('/delete', jsonParser, function (request, response) {
+router.post('/delete', jsonParser, validateAvatarUrlMiddleware, function (request, response) {
     const dirName = String(request.body.avatar_url).replace('.png', '');
     const fileName = String(request.body.chatfile);
     const filePath = path.join(request.user.directories.chats, dirName, sanitize(fileName));
@@ -388,7 +389,7 @@ router.post('/delete', jsonParser, function (request, response) {
     return response.send('ok');
 });
 
-router.post('/export', jsonParser, async function (request, response) {
+router.post('/export', jsonParser, validateAvatarUrlMiddleware, async function (request, response) {
     if (!request.body.file || (!request.body.avatar_url && request.body.is_group === false)) {
         return response.sendStatus(400);
     }
@@ -478,7 +479,7 @@ router.post('/group/import', urlencodedParser, function (request, response) {
     }
 });
 
-router.post('/import', urlencodedParser, function (request, response) {
+router.post('/import', urlencodedParser, validateAvatarUrlMiddleware, function (request, response) {
     if (!request.body) return response.sendStatus(400);
 
     const format = request.body.file_type;
@@ -626,7 +627,7 @@ router.post('/group/save', jsonParser, (request, response) => {
     return response.send({ ok: true });
 });
 
-router.post('/search', jsonParser, function (request, response) {
+router.post('/search', jsonParser, validateAvatarUrlMiddleware, function (request, response) {
     try {
         const { query, avatar_url, group_id } = request.body;
         let chatFiles = [];
diff --git a/src/endpoints/settings.js b/src/endpoints/settings.js
index 3cc7e3bec..4df4978cc 100644
--- a/src/endpoints/settings.js
+++ b/src/endpoints/settings.js
@@ -9,6 +9,7 @@ import { SETTINGS_FILE } from '../constants.js';
 import { getConfigValue, generateTimestamp, removeOldBackups } from '../util.js';
 import { jsonParser } from '../express-common.js';
 import { getAllUserHandles, getUserDirectories } from '../users.js';
+import { getFileNameValidationFunction } from '../middleware/validateFileName.js';
 
 const ENABLE_EXTENSIONS = !!getConfigValue('extensions.enabled', true);
 const ENABLE_EXTENSIONS_AUTO_UPDATE = !!getConfigValue('extensions.autoUpdate', true);
@@ -296,7 +297,7 @@ router.post('/get-snapshots', jsonParser, async (request, response) => {
     }
 });
 
-router.post('/load-snapshot', jsonParser, async (request, response) => {
+router.post('/load-snapshot', jsonParser, getFileNameValidationFunction('name'), async (request, response) => {
     try {
         const userFilesPattern = getFilePrefix(request.user.profile.handle);
 
@@ -330,7 +331,7 @@ router.post('/make-snapshot', jsonParser, async (request, response) => {
     }
 });
 
-router.post('/restore-snapshot', jsonParser, async (request, response) => {
+router.post('/restore-snapshot', jsonParser, getFileNameValidationFunction('name'), async (request, response) => {
     try {
         const userFilesPattern = getFilePrefix(request.user.profile.handle);
 
diff --git a/src/middleware/validateFileName.js b/src/middleware/validateFileName.js
new file mode 100644
index 000000000..ccfb0e88d
--- /dev/null
+++ b/src/middleware/validateFileName.js
@@ -0,0 +1,34 @@
+import path from 'node:path';
+
+/**
+ * Gets a middleware function that validates the field in the request body.
+ * @param {string} fieldName Field name
+ * @returns {import('express').RequestHandler} Middleware function
+ */
+export function getFileNameValidationFunction(fieldName) {
+    /**
+    * Validates the field in the request body.
+    * @param {import('express').Request} req Request object
+    * @param {import('express').Response} res Response object
+    * @param {import('express').NextFunction} next Next middleware
+    */
+    return function validateAvatarUrlMiddleware(req, res, next) {
+        if (req.body && fieldName in req.body && typeof req.body[fieldName] === 'string') {
+            const forbiddenRegExp = path.sep === '/' ? /[/\x00]/ : /[/\x00\\]/;
+            if (forbiddenRegExp.test(req.body[fieldName])) {
+                console.error('An error occurred while validating the request body', {
+                    handle: req.user.profile.handle,
+                    path: req.originalUrl,
+                    field: fieldName,
+                    value: req.body[fieldName],
+                });
+                return res.sendStatus(400);
+            }
+        }
+
+        next();
+    };
+}
+
+const avatarUrlValidationFunction = getFileNameValidationFunction('avatar_url');
+export default avatarUrlValidationFunction;