2012 — Groupon: An ongoing flaw in Groupon's email link encryption…
Data compromised
Personal information
Technical writeup
An ongoing flaw in Groupon's email link encryption exposes the emails of some Groupon users when specific terms are added into Google searches of Groupon's site. Groupon believes that the problem is caused by users publicly pasting their Groupon deals online. Groupon is working on a solution to exclude the results.
Root cause
Unintended disclosure