use beforeWrite method of CollectionFS instead of collection-hooks

models/attachments.js

@@ -3,7 +3,24 @@ Attachments = new FS.Collection('attachments', {
 
     // XXX Add a new store for cover thumbnails so we don't load big images in
     // the general board view
-    new FS.Store.GridFS('attachments'),
+    new FS.Store.GridFS('attachments', {
+      // If the uploaded document is not an image we need to enforce browser
+      // download instead of execution. This is particularly important for HTML
+      // files that the browser will just execute if we don't serve them with the
+      // appropriate `application/octet-stream` MIME header which can lead to user
+      // data leaks. I imagine other formats (like PDF) can also be attack vectors.
+      // See https://github.com/wekan/wekan/issues/99
+      // XXX Should we use `beforeWrite` option of CollectionFS instead of
+      // collection-hooks?
+      // We should use `beforeWrite`.
+      beforeWrite: (fileObj) => {
+        if (!fileObj.isImage()) {
+          return {
+            type: 'application/octet-stream'
+          };
+        }
+      },
+    }),
   ],
 });
 
@@ -36,23 +53,6 @@ if (Meteor.isServer) {
 
 // XXX Enforce a schema for the Attachments CollectionFS
 
-Attachments.files.before.insert((userId, doc) => {
-  const file = new FS.File(doc);
-  doc.userId = userId;
-
-  // If the uploaded document is not an image we need to enforce browser
-  // download instead of execution. This is particularly important for HTML
-  // files that the browser will just execute if we don't serve them with the
-  // appropriate `application/octet-stream` MIME header which can lead to user
-  // data leaks. I imagine other formats (like PDF) can also be attack vectors.
-  // See https://github.com/wekan/wekan/issues/99
-  // XXX Should we use `beforeWrite` option of CollectionFS instead of
-  // collection-hooks?
-  if (!file.isImage()) {
-    file.original.type = 'application/octet-stream';
-  }
-});
-
 if (Meteor.isServer) {
   Attachments.files.after.insert((userId, doc) => {
     Activities.insert({