Steps to replicate :

1. Login to Confluence
2. Copy the text generated from the following page to a Confluence page to the point where you would need to scroll :
   http://www.lipsum.com/feed/html
3. After adding the text, please scroll to the bottom of the editor
4. Click on the menu key, you can find the picture of the menu key in case you have trouble finding it :
   

Current behavior : the cursor jump to the top of editor
Expected behavior : the cursor should not jump to the top of the editor and should open normal internet browser context menu (like you would have pressed a right click in a web page).