A Longitudinal Study of Vulnerable Client-side Resources and Web Developers' Updating Behaviors

Modern Websites rely on various client-side web resources, such as JavaScript libraries, to provide end-users with rich and interactive web experiences. Unfortunately, anecdotal evidence shows that improperly managed client-side resources could open up attack surfaces that adversaries can exploit. However, there is still a lack of a comprehensive understanding of the updating practices among web developers and the potential impact of inaccuracies in Common Vulnerabilities and Exposures (CVE) information on the security of the web ecosystem. In this paper, we conduct a longitudinal (four-year) measurement study of the security practices and implications on client-side resources (e.g., JavaScript libraries and Adobe Flash) across the Web. Specifically, we first collect a large-scale dataset of 157.2M webpages of Alexa Top 1M websites for four years in the wild. Analyzing the dataset, we find an average of 41.2% of websites (in each year of the four years) carry at least one vulnerable client-side resource (e.g., JavaScript or Adobe Flash). We also reveal that vulnerable JavaScript library versions are frequently observed in the wild, suggesting a concerning level of lagging update practice in the wild. On average, we observe 531.2 days with 25,337 websites of the window of vulnerability due to the unpatched client-side resources from the release of security patches. Furthermore, we manually investigate the fidelity of CVE (Common Vulnerabilities and Exposures) reports on client-side resources, leveraging PoC (Proof of Concept) code. We find that 13 CVE reports (out of 27) have incorrect vulnerable version information, which may impact security-related tasks such as security updates.