When you simulate a call using a third party software the message "All OK" appears on a new browser window.
SAP Hybris Cloud for Customer 1802 / 02 and future version
The "All OK" message is the HTTP response returned by the CTI adapter to advise that the request has been successfully completed.
This is the system expected behavior.
Please check with your third party software the possibility to hide this response from their side.
CTI; All OK; HTTP; Response; , KBA , LOD-CRM-LA , Live Activity , How To