If you see a "This link has expired" or "Are you sure you want to do this?" message when installing a plugin

When installing a plugin, if you see a message that says "This link has expired" or "Are you sure you want to do this? Please try again?", the issue is the server's file upload size limit. The problem can be resolved by increasing the file upload limit.

How to increase the file upload limit?

To resolve this, please follow the steps in this article that relate to your server setup.