Funny thing is, I didn’t do anything specific to WordPress. The index.php file has the same creation/modification date as other PHP files in the directory, so I don’t believe it has been modified.
The only thing that I did on the server was upgrade to PHP version 5.4.14. Other than that, I haven’t modified the WordPress install or even the page content.
I can access https://breatoastmasters.org/wp-login.php and wp-admin just fine…I can even log in to the admin area, but the problem seems to be with the index.php file, or one of the files that it calls.