Recently, Drupal 7 had quite a massive and unique SQL injection vulnerability.
Luckily, Drupal also has an awesome security team, and a security mailinglist, where they announced the vulnerability and how to fix it.

For clients:
I am closely following the Drupal security mailinglist, and apply security updates based on the risk level.
And luckily I did not miss the highly critical https://www.drupal.org/SA-CORE-2014-005.

All Drupal 7 sites that I am involved with are now upgraded to '7.32, or I warned whoever is maintaining the site.
If anything still goes wrong with those sites, it must be something else.

For other developers / site maintainers:
Please make sure you actually upgrade to 7.32, not to 7.31. "drush up drupal" can trick you. Or

@bartfeenstra @ajschwab @brain4lunch @drupal be sure to flush cache_update first

— larowlan (@larowlan) 15. Oktober 2014