Pages and posts in WordPress can be published password protected and then display a password form before showing the content.

In some cases, trying to submit the password in the login form leads to a 404 error page. It seems to only happen on multi language sites that have WPML set to use subdirectories for languages.

To reproduce:

• Create a page or post (on a multi language site with WPML)
• Set visibility to password protected
• Open the newly created page/post
• Enter the password and submit

Expected result:

The page content is shown

Actual result:

A 404 error is shown (from nginx, not the usual 404 page)

Note:

I'm not sure this is WPML specific or if it affects other translation plugins as well