A logic issue was addressed with improved validation. This issue is fixed in iOS 12.2, tvOS 12.2, Safari 12.1, iTunes 12.9.4 for Windows, iCloud for Windows 7.11. A malicious website may be able to execute scripts in the context of another website.
https://support.apple.com/HT209599
https://support.apple.com/HT209601
https://support.apple.com/HT209603
Source: MITRE
Published: 2019-12-18
Updated: 2019-12-31
Type: CWE-20
Base Score: 9.3
Vector: AV:N/AC:M/Au:N/C:C/I:C/A:C
Impact Score: 10
Exploitability Score: 8.6
Severity: HIGH
Base Score: 8.8
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Impact Score: 5.9
Exploitability Score: 2.8
Severity: HIGH