A malicious web page could open a tel link in a window that was showing a different website, causing the phone-call prompt to appear as if that site had requested the call. This vulnerability was fixed in Firefox for iOS 156.1.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
Required
User action required
Impact Assessment
Confidentiality
Low
Partial data leak
Integrity
None
No data modification
Availability
Low
Partial disruption
CVSS Vector v3.1