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Background Note: Appearing at USENIX Security’22, the report Leaky Forms: A Study of Email and Password Exfiltration Before Form Submission notes that email addresses—or identifiers derived from them—are known to be used by data brokers and advertisers for cross-site, cross-platform, and persistent identification of potentially unsuspecting individuals. In order to find out whether access to online forms is misused by online trackers, the authors of this new report present a measurement of email and password collection that occur before form submission on the top 100K websites. Given the potential privacy and security implications of leaky forms, this research may be beneficial for cybersecurity, information governance, and legal discovery professionals seeking to better understand the challenges and consequences of email and password exfiltration prior to form submissions.

Research Report*

Leaky Forms: A Study of Email and Password Exfiltration Before Form Submission

By Asuman Senol, Gunes Acar, Mathias Humbert, and Frederik Zuiderveen Borgesius

Report Abstract

Web users enter their email addresses into online forms for a variety of reasons, including signing in or signing up for a service, or subscribing to a newsletter. While enabling such functionality, email addresses typed into forms can also be collected by third-party scripts even when users change their minds and leave the site without submitting the form. Email addresses—or identifiers derived from them—are known to be used by data brokers and advertisers for cross-site, cross-platform, and persistent identification of potentially unsuspecting individuals. In order to find out whether access to online forms is misused by online trackers, we present a measurement of email and password collection that occurs before the form submission on the top 100,000 websites. We evaluate the effect of user location, browser configuration, and inter-action with consent dialogs by comparing results across two vantage points (EU/US), two browser configurations (desktop/mobile), and three consent modes. Our crawler finds and fills email and password fields, monitors the network traffic for leaks, and intercepts script access to filled input fields. Our analyses show that users’ email addresses are exfiltrated to tracking, marketing, and analytics domains before form submission and without giving consent on 1,844 websites in the EU crawl and 2, 950 websites in the US crawl. While the majority of email addresses are sent to known tracking domains, we further identify 41 tracker domains that are not listed by any of the popular blocklists. Furthermore, we find incidental password collection on 52 websites by third-party session replay scripts.

Report Conclusion

We presented a large-scale study of email and password exfiltration by online trackers before form submission. In order to address the challenges of finding and filling input fields, we integrated into our crawler a pre-trained ML classifier that detects email fields. Our results—likely lower bounds—show that on thousands of sites email addresses are collected from login, registration, and newsletter subscription forms; and sent to trackers before users submit any form or give their consent. Further, we found tens of sites where passwords are incidentally collected by third parties providing session replay services. Comparing results from the EU and the US vantage points, we found that 60% more websites leaked users’ emails to trackers, when visited from the US. Measuring the effect of consent choices on the exfiltration, we found their effect to be minimal. Based on our findings, users should assume that the personal information they enter into web forms may be collected by trackers—even if the form is never submitted. Considering its scale, intrusiveness, and unintended side effects, the privacy problem we investigate deserves more attention from browser vendors, privacy tool developers, and data protection agencies.

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Complete Report – Leaky Forms: A Study of Email and Password Exfiltration Before Form Submission (PDF) – Mouseover to Scroll

Leaky Forms- A Study of Email and Password Exfiltration Before Form Submission

Read the original paper.


*Shared as Open Access Media by USENIX – The Advanced Computing Systems Association.

Reference: @inproceedings, 2022. Leaky Forms: A Study of Email and Password Exfiltration Before Form Submission. 31st USENIX Security Symposium (USENIX Security 22). [online] USENIX Association. Available at: <https://www.usenix.org/system/files/sec22fall_senol.pdf> [Accessed 16 May 2022].

Additional Reading

Source: ComplexDiscovery

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