This needs to be tested in a site with MDL-57389 fixed. In Moodle 3.3 web, login as admin and add a remote CSS (Site administration > Mobile app > Mobile appearance > mobilecssurl). Sample CSS: https://gist.githubusercontent.com/jleyva/5d2f265a833a2122f3be/raw/294141fcc19499a3997cc9355ba3c10a74c45a8f/moodlemobileapp.css In the app, click to add a site, enter the site URL and click "Connect". Check that your styles are loaded in the credentials screen. Click to go back to the site URL view. Check that the styles aren't loaded anymore. Enter to the credentials screen again and login in the site. Check that the site is loaded and there is no "blink" effect in the styles (you always see your custom styles). Logout and now add a site without a custom CSS. Check that the styles used during all the process are the default ones.