PREVENTING LEAKAGE OF COOKIE DATA

Disclosed are various embodiments for preventing the unintended leakage of cookie data between network sites using a shared high-level domain and vice versa. In one embodiment, a browser application stores data from a first network site having a high-level domain in a client computing device. Access to the data is limited to one or more network sites having the high-level domain. A first classification is assigned to the first network site. A second classification is assigned to a second network site having the high-level domain. The data is sent to the second network site in response to determining that the first classification matches the second classification.