A publicity stunt is an event designed to attract the public's attention to the promoters or their causes. Publicity stunts can be professionally organised or set up by amateurs.
This also makes clear that many publicity stunts try to exploit succès de scandale mechanisms for attracting attention.
Many people would maintain that attempts to raise awareness of serious causes are not "stunts". That depends on the point of view of the observer.
A distinction could be to label stunts as events specifically designed to attract publicity. Events with a particular objective that only incidentally attract publicity can be exempted from the term. For instance, if an animal rights activist were to rescue a dancing bear in India and that action became known through a report on a court case, that would not be a publicity stunt. If however, the activist arranged for the press to cover the rescue, it would be a publicity stunt.