Updating modules in Drupal 8 is similar to updating modules in Drupal 7 - the drush pm-update (drush up) command still works, but there's a new "gotcha" that you need to look out for when updating modules that work with entities. 

Sometimes, after updating modules that interact with entities, you'll see a "Entity/field definitions: Mismatched entity and/or field definitions" error on your site's status report (admin/reports/status). 

In the screenshot above, this error was generated by updating the Inline Entity Form module from its alpha4 version to the most recent -dev version (the site also uses the Scheduled Updates module). As long as a mismatch is present, the fields listed in the error will lead to unpredictable results.

Neither rebuilding caches nor running cron will fix this issue ("drush up" doesn't automatically run this command either) - for these types of errors, the drush entity-updates command is what you're looking for.

Once this command is run, your status report will look something like this:

This is just one more reason why checking your site's status report page after updating modules is always a good idea.