Issue with static files and session on Firefox 76.0.1

Steps to reproduce

1. Launch test project
2. Open 127.0.0.1:8080
3. Reload the page and look at the console (should print Count: 0)
4. Open network tab in dev tools
5. Right click on image and click "Open in New Tab"
6. Reload page with opened image
7. Look at the console again

Expected result

Count is incremented by 1

Actual result

Count is zero