ShowIP is designed to show the IP address of the current page in the status bar. It also allows querying custom information services by IP (right click) and hostname (left click), like whois, netcraft, etc. Currently over 170,000 people are said to be using the add-on. Since version 1.3 (released on April 19th 2012) it has also sent data to a third-party server, including sensitive data which could identify individuals or reduce their security.”]
Source: https://grahamcluley.com/privacy-concern-showip-firefox-add-on/