I've recently noticed that new windows of Firefox keep opening with the first bookmark from the first tab, repeatedly and without user intervention

It creates thumbnails for tiles. In new WebEx Mozilla removed functionality that we used before. You can set dials to manual previews like Gallery images or your own images.

If it takes your cursor out when you're typing - we will fix it in the next update soon

Thank you for your reply.

The behavior I notice is that Firefox opens a new window in the background and it happens to be the exact page that is set for the first tile of the first of 3 tabs that I've created. Something is repeatedly opening this tile as a new window in the background and then usually closing it immediately or shortly after. It's very annoying because it steals focus so if I am typing, I am interrupted and I need to click on the text box in my current browser to continue to type. My anti-virus program says I'm in the clear, and it's quite the coincidence that the window opens to a bookmark that I have set as a tile, so I assume it is this plugin that is causing this strange behavior.

I have a lot of tiles set up so I would like to avoid an uninstall.

I've discovered that editing the tile and deselecting "Auto Update" has resolved the issue. If you'd like to try to replicate this strange bug, create a tile with a google maps bookmark showing a specific location and set it to create a thumbnail from the page, leaving auto-update activated, refreshing every 1 minute. 

Thank you, we will check it.