A vulnerability in the Web Access feature of Cisco IP Phones Series 7800 and Series 8800 could allow an unauthenticated, remote attacker to view sensitive information on an affected device. The vulnerability is due to improper access controls on the web-based management interface of an affected device. An attacker could exploit this vulnerability by sending malicious requests to the device, which could allow the attacker to bypass access restrictions. A successful attack could allow the attacker to view sensitive information, including device call logs that contain names, usernames, and phone numbers of users of the device.
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-phone-logs-2O7f7ExM