The collapse of social contexts has been amplified by digital infrastructures but surprisingly received insufficient attention from Web privacy scholars. Users are persistently identified within and across distinct web contexts, in varying degrees, through and by different websites and trackers, losing the ability to maintain a fragmented identity. To systematically evaluate this structural privacy harm we operationalize the theory of Privacy as Contextual Integrity and measure persistent user identification within and between distinct Web contexts. We crawl the top-700 popular websites across the contexts of health, finance, news & media, LGBTQ, eCommerce, adult, and education websites, for 27 days, to learn how persistent browser identification via third-party cookies and JavaScript fingerprinting is diffused within and between web contexts. Past work measured Web tracking in bulk, highlighting the volume of trackers and tracking techniques. These measurements miss a crucial privacy implication of Web tracking - the collapse of online contexts. Our findings reveal how persistent browser identification varies between and within contexts, diffusing user IDs to different distances, contrasting known tracking distributions across websites, and conducted as a joint or separate effort via cookie IDs and JS fingerprinting. Our network analysis can inform the construction of browser storage containers to protect users against real-time context collapse. This is a first modest step in measuring Web privacy as contextual integrity, opening new avenues for contextual Web privacy research.

翻译：社交情境的崩塌在数字基础设施中被放大，但令人惊讶的是，网络隐私学者对此关注不足。用户在不同程度上通过不同网站和追踪器在相异的网络情境内部及之间被持续识别，从而丧失了维持碎片化身份的能力。为系统评估这种结构性隐私损害，我们将“隐私即情境完整性”理论操作化，并测量相异网络情境内部及之间的持久用户识别。我们连续27天爬取健康、金融、新闻与媒体、LGBTQ、电子商务、成人及教育等情境下的前700个热门网站，以研究通过第三方Cookie和JavaScript指纹识别实现的持久浏览器识别如何在网络情境内部及之间扩散。以往研究批量测量网络追踪，侧重于追踪器数量和追踪技术。这些测量忽略了网络追踪的一个关键隐私影响——在线情境的崩塌。我们的研究结果揭示了持久浏览器识别如何在情境之间及内部变化，用户ID以不同距离扩散，与已知的跨网站追踪分布形成对比，并通过Cookie ID和JS指纹识别以联合或单独的方式进行。我们的网络分析可为构建浏览器存储容器提供参考，以保护用户免受实时情境崩塌的影响。这是测量基于情境完整性的网络隐私的初步尝试，为情境化网络隐私研究开辟了新途径。