Try http or a browser that does not "protect" you.
https://bugzilla.wikimedia.org/show_bug.cgi?id=49698

• This bug has been marked as a duplicate of bug 49698 ***

I guess one bug is caused by https://gerrit.wikimedia.org/r/#/c/75122/
Looking for a solution.

For clarification, there are 3 issues involved:

1. Firefox and other modern browsers do not allow connections to HTTP while being on HTTPS. To overcome this problem, either use HTTP (Preferences > user profile > basic information > uncheck "Always use a secure connection when logged in") or allow HTTP traffic from your browser's options.
2. There was a file input shown when clicking the textbox for entering a Flickr URL. This is because UploadWizard does not hide the transparent file input after selecting the "Flickr-option". https://gerrit.wikimedia.org/r/#/c/75122/ possibly unearthed this fault by stopping to move the file input around.
3. Sometimes CSS seems to be later loaded. Therefore, the values calculated in moveFileInputToCover are correct for the rendering without that CSS but not with. Consequently the file input only partially covers the button. This does not happen reproducibly and only when users skip the tutorial.

Change 81660 had a related patch set uploaded by Rillke:
Using "poll" as positioning method for first file input

https://gerrit.wikimedia.org/r/81660

1. can be fixed by the user and has nothing to do with https://gerrit.wikimedia.org/r/#/c/75122/
2. was fixed locally for the time being (https://commons.wikimedia.org/w/index.php?title=MediaWiki%3ACommon.css&diff=102893482&oldid=102168173)
3. should be fixed as soon as possible as it may affect a lot of users

Change 81660 merged by jenkins-bot:
Using "poll" as positioning method for first file input

https://gerrit.wikimedia.org/r/81660

The patch I merged seems to fix this issue. Thanks very much to Rillke for intercepting and responding so quickly :)

Reopen if the problem is not fixed on Commons once it's deployed.