The (Un)usual Suspects - Studying Reasons for Lacking Updates in WordPress

—The widespread use of Content Management Systems (CMS) like WordPress has made these systems attractive targets for adversaries, with the vulnerabilities in the code posing serious risks. Despite being the most effective way to reduce these risks, more than half of all CMS installations lack the latest security patches. Researchers have tried to notify website operators about vulnerabilities using vulnerability notifications, which often exhibit limited impact. In this paper, we use the Grounded Theory approach to investigate the reasons why website owners do not update their CMS. To gain a holistic view on lacking update behavior, we interviewed website owners with outdated WordPress-based systems as well as individuals involved in website creation and hosting. On the one hand, we could confirm issues known from other ecosystems, such as lack of risk awareness, perceived risks of updates, and update costs, as factors for lacking CMS updates. More importantly, our study identified factors that have not been explicitly addressed in the general updating behaviour and vulnerability notification literature: (1) the subjective value of a website to its owner and (2) the delegation of website operations, which influence updating behavior far more decisively. Furthermore, we showed that website owners perceive a potential compromise of their CMS only as a risk to themselves and not as a threat to the wider online community. These findings that we present as four non-update scenarios may partly explain the limited success of previous efforts to notify operators about vulnerabilities in their systems. Our study not only offers valuable insights for future research, testing the effectiveness of vulnerability notifications and studying updating behavior in general, but it also proposes practical suggestions on how to reduce the number of outdated systems on the web.