diff --git a/spec/FilesController.spec.js b/spec/FilesController.spec.js
index ad3a40e7557..3dc11a79f5a 100644
--- a/spec/FilesController.spec.js
+++ b/spec/FilesController.spec.js
@@ -14,6 +14,7 @@ const mockAdapter = {
   deleteFile: () => {},
   getFileData: () => {},
   getFileLocation: () => 'xyz',
+  validateFilename: () => {},
 };
 
 // Small additional tests to improve overall coverage
@@ -118,4 +119,13 @@ describe('FilesController', () => {
 
     done();
   });
+
+  it('should reject slashes in file names', done => {
+    const gridStoreAdapter = new GridFSBucketAdapter(
+      'mongodb://localhost:27017/parse'
+    );
+    const fileName = 'foo/randomFileName.pdf';
+    expect(gridStoreAdapter.validateFilename(fileName)).not.toBe(null);
+    done();
+  });
 });
diff --git a/src/Adapters/Files/FilesAdapter.js b/src/Adapters/Files/FilesAdapter.js
index db02174ca6e..1bf3d287152 100644
--- a/src/Adapters/Files/FilesAdapter.js
+++ b/src/Adapters/Files/FilesAdapter.js
@@ -8,12 +8,15 @@
 // * deleteFile(filename)
 // * getFileData(filename)
 // * getFileLocation(config, filename)
+// Adapter classes should implement the following functions:
+// * validateFilename(filename)
 //
 // Default is GridFSBucketAdapter, which requires mongo
 // and for the API server to be using the DatabaseController with Mongo
 // database adapter.
 
 import type { Config } from '../../Config';
+import Parse from 'parse/lib/node/Parse';
 /**
  * @module Adapters
  */
@@ -56,6 +59,37 @@ export class FilesAdapter {
    * @return {string} Absolute URL
    */
   getFileLocation(config: Config, filename: string): string {}
+
+  /** Validate a filename for this adaptor type (optional)1G
+   *
+   * @param {string} filename
+   *
+   * @returns {null|*|Parse.Error} null if there are no errors
+   */
+  // TODO: Make this required once enough people have updated their adaptors
+  // validateFilename(filename): ?Parse.Error {}
+}
+
+/**
+ * Default filename validate pulled out of FilesRouter.  Mostly used for Mongo storage
+ *
+ * @param filename
+ * @returns {null|*|Parse.Error|Parse.ParseError|ParseError|ParseError|Parse.ParseError}
+ */
+export function validateFilename(filename): ?Parse.Error {
+  if (filename.length > 128) {
+    return new Parse.Error(Parse.Error.INVALID_FILE_NAME, 'Filename too long.');
+  }
+
+  // US/ASCII centric default
+  const regx = /^[_a-zA-Z0-9][a-zA-Z0-9@. ~_-]*$/;
+  if (!filename.match(regx)) {
+    return new Parse.Error(
+      Parse.Error.INVALID_FILE_NAME,
+      'Filename contains invalid characters.'
+    );
+  }
+  return null; // No errors
 }
 
 export default FilesAdapter;
diff --git a/src/Adapters/Files/GridFSBucketAdapter.js b/src/Adapters/Files/GridFSBucketAdapter.js
index bc1b4ae920c..28b238efe38 100644
--- a/src/Adapters/Files/GridFSBucketAdapter.js
+++ b/src/Adapters/Files/GridFSBucketAdapter.js
@@ -8,7 +8,7 @@
 
 // @flow-disable-next
 import { MongoClient, GridFSBucket, Db } from 'mongodb';
-import { FilesAdapter } from './FilesAdapter';
+import { FilesAdapter, validateFilename } from './FilesAdapter';
 import defaults from '../../defaults';
 
 export class GridFSBucketAdapter extends FilesAdapter {
@@ -139,6 +139,10 @@ export class GridFSBucketAdapter extends FilesAdapter {
     }
     return this._client.close(false);
   }
+
+  validateFilename(filename) {
+    return validateFilename(filename);
+  }
 }
 
 export default GridFSBucketAdapter;
diff --git a/src/Adapters/Files/GridStoreAdapter.js b/src/Adapters/Files/GridStoreAdapter.js
index 3eb50ee5614..3d6bba10724 100644
--- a/src/Adapters/Files/GridStoreAdapter.js
+++ b/src/Adapters/Files/GridStoreAdapter.js
@@ -9,7 +9,7 @@
 
 // @flow-disable-next
 import { MongoClient, GridStore, Db } from 'mongodb';
-import { FilesAdapter } from './FilesAdapter';
+import { FilesAdapter, validateFilename } from './FilesAdapter';
 import defaults from '../../defaults';
 
 export class GridStoreAdapter extends FilesAdapter {
@@ -110,6 +110,10 @@ export class GridStoreAdapter extends FilesAdapter {
     }
     return this._client.close(false);
   }
+
+  validateFilename(filename) {
+    return validateFilename(filename);
+  }
 }
 
 // handleRangeRequest is licensed under Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/).
diff --git a/src/Controllers/FilesController.js b/src/Controllers/FilesController.js
index 579e3e43d6e..63c259931bc 100644
--- a/src/Controllers/FilesController.js
+++ b/src/Controllers/FilesController.js
@@ -1,7 +1,7 @@
 // FilesController.js
 import { randomHexString } from '../cryptoUtils';
 import AdaptableController from './AdaptableController';
-import { FilesAdapter } from '../Adapters/Files/FilesAdapter';
+import validateFilename, { FilesAdapter } from '../Adapters/Files/FilesAdapter';
 import path from 'path';
 import mime from 'mime';
 
@@ -95,6 +95,13 @@ export class FilesController extends AdaptableController {
   handleFileStream(config, filename, req, res, contentType) {
     return this.adapter.handleFileStream(filename, req, res, contentType);
   }
+
+  validateFilename(filename) {
+    if (typeof this.adapter.validateFilename === 'function') {
+      return this.adapter.validateFilename(filename);
+    }
+    return validateFilename(filename);
+  }
 }
 
 export default FilesController;
diff --git a/src/Routers/FilesRouter.js b/src/Routers/FilesRouter.js
index 72d032afa72..56fb5a3cc8b 100644
--- a/src/Routers/FilesRouter.js
+++ b/src/Routers/FilesRouter.js
@@ -69,6 +69,11 @@ export class FilesRouter {
   }
 
   createHandler(req, res, next) {
+    const config = req.config;
+    const filesController = config.filesController;
+    const filename = req.params.filename;
+    const contentType = req.get('Content-type');
+
     if (!req.body || !req.body.length) {
       next(
         new Parse.Error(Parse.Error.FILE_SAVE_ERROR, 'Invalid file upload.')
@@ -76,28 +81,12 @@ export class FilesRouter {
       return;
     }
 
-    if (req.params.filename.length > 128) {
-      next(
-        new Parse.Error(Parse.Error.INVALID_FILE_NAME, 'Filename too long.')
-      );
+    const error = filesController.validateFilename(filename);
+    if (error) {
+      next(error);
       return;
     }
 
-    if (!req.params.filename.match(/^[_a-zA-Z0-9][a-zA-Z0-9@\.\ ~_-]*$/)) {
-      next(
-        new Parse.Error(
-          Parse.Error.INVALID_FILE_NAME,
-          'Filename contains invalid characters.'
-        )
-      );
-      return;
-    }
-
-    const filename = req.params.filename;
-    const contentType = req.get('Content-type');
-    const config = req.config;
-    const filesController = config.filesController;
-
     filesController
       .createFile(config, filename, req.body, contentType)
       .then(result => {