It appears Evernote are the latest in a string of attacks, with their Operations & Security team discovering, and blocking suspicious activity on their network. The attempted attack appears to be a coordinated attempt to gain access to Evernote's network.
In order to keep your data safe, Evernote have enabled a server-wide password reset - meaning that everyone will need to change their password before they log into their Evernote account. Evernote's network was compromised, with the investigation in place reporting that the hackers gained access to Evernote users' information, such as usernames, emails and even encrypted passwords. The passwords were protected by one-way encryption, which keeps them much safer than normal.
Evernote would still like to play it safe, which is where the server-wide password reset comes into play.