The Composer is a part of Drupal 8.2 core and if you run it to update dependancies or update itself, it updates its files inside /vendor/composer/ or composer.json in root dir and then Hacked! screams that files were changed! And new user start panicking his website got hacked.
Read more about Drupal 8 and Composer
https://www.drupal.org/node/2404989 →
https://www.drupal.org/node/2718229 →
Active
Code
Not all content is available!
It's likely this issue predates Contrib.social: some issue and comment data are missing.