Permission Denied When Opening Local Files in Web Browsers

I've run into a bit of a weird issue: If I try to open a file-local .html file inside of a directory starting with a dot (.) the browser claims that it does not have permission to view it, e.g.:

mkdir -p ~/.test/
echo "Hello, World!" > ~/.test/test.html
chmod -R 777 ~/.test/
firefox ~/.test/test.html    # Works on Ubuntu 21.10 but not in 22.04.
chromium ~/.test/test.html   # Fails on Ubuntu 21.10 and 22.04.

Is this some kind of browser sandboxing issue? And if so, is there some common workaround in place? One thing that I did note about Firefox: Ubuntu has moved to a snap package in 22.04, is that somehow related to these permissions? Additionally, Chromium appears to also be a snap package (in both cases).