CSChecker: Revisiting GDPR and CCPA Compliance of Cookie Banners on the Web

Privacy regulations like GDPR and CCPA have greatly affected online advertising and tracking strategies. To comply with the regulations, websites need to display consent management UIs (i.e., cookie banners) implemented under the corresponding technical frameworks, allowing users to specify consents regarding their personal data processing. Although prior works have investigated the cookie banner compliance problems with GDPR, the technical specification has significantly changed. The compliance status under the latest framework remains unclear. There also lacks a systematic study of CCPA banner compliance. More importantly, most work have focused on detecting the regulation violations, whereas little is known about the possible culprits and causes. In this paper, we develop CSChecker, a browser-based tool that monitors and records consent strings on websites. We use CSChecker to analyze the GDPR and CCPA cookie banners, and reveal previously unknown compliance problems under both frameworks. We also discover and analyze possible miscreants leading to the violations, e.g., consent management providers that return wrong consent data. The comparison of the two frameworks inspires several suggestions about the design of cookie banners, the implementation of opt-out mechanisms, and the enforcement of user consent choices. CCS CONCEPTS • Security and privacy → Privacy protections.