Can a 500 error be caused by a plugin or extension?

Yes, a 500 error is a very common symptom of a problematic plugin or extension, particularly in CMS platforms like WordPress, Joomla, and Drupal. A poorly coded plugin, a conflicting plugin, or an outdated plugin can easily trigger 500 errors. Deactivating plugins one by one is a standard troubleshooting technique to isolate the culprit.