Warns users that their form (quickform) session is about to expire.
Quickform forms include the Event Registration page or Contribution page. Forms such as those created with AngularJS/Aafform or other frameworks are not affected.
A typical symptom of these errors is when CiviCRM will randomly have a fatal error when a form is submitted, with an error message such as "missing params" or "could not find id". This happens often if, for example, the user opened a form, switched tasks, then comes back 20 minutes later and tries filling in and submitting the form.