Keyboard Surfing addon will not collect, log or send any of your data or data about web pages you visit. In fact, it will not send any data at all.

Keyboard Surfing addon needs to inspect every web page you visit (to find links).

Keyboard Surfing addon needs to inject a few HTML elements into pages you visit (the red dot, the red box and the help screen). It will not modify other parts of a web page.