diff --git a/app/assets/javascripts/discourse/components/composer-editor.js.es6 b/app/assets/javascripts/discourse/components/composer-editor.js.es6
index c5113a20cf4..f16acd43b9a 100644
--- a/app/assets/javascripts/discourse/components/composer-editor.js.es6
+++ b/app/assets/javascripts/discourse/components/composer-editor.js.es6
@@ -296,7 +296,13 @@ export default Ember.Component.extend({
   // Believe it or not pasting an image in Firefox doesn't work without this code
   _firefoxPastingHack() {
     const uaMatch = navigator.userAgent.match(/Firefox\/(\d+)\.\d/);
-    if (uaMatch && parseInt(uaMatch[1]) >= 24) {
+    if (uaMatch) {
+      let uaVersion = parseInt(uaMatch[1]);
+      if (uaVersion < 24 || 50 <= uaVersion) {
+        // The hack is no longer required in FF 50 and later.
+        // See: https://bugzilla.mozilla.org/show_bug.cgi?id=906420
+        return;
+      }
       this.$().append( Ember.$("<div id='contenteditable' contenteditable='true' style='height: 0; width: 0; overflow: hidden'></div>") );
       this.$("textarea").off('keydown.contenteditable');
       this.$("textarea").on('keydown.contenteditable', event => {