Is using cookies from a web-browser a sane rationale for desktop application development?

I am looking at making an application that would make OpenID authentication with desktop clients easy. The rationale is to steal the cookies from the web-browser, so as to avoid having to hard-code authentication to every possible OpenID provider. Assuming the user has already logged on to the OpenID provider, the application clones the cookies from the default browser, and requests authentication to the desired service with the appropriate OpenID URL. To make this application usable, I need to know what are the most commonly used web browsers used on Linux, possibly with statistical evidence. I assume that Firefox and Chromium are the two most popular at the moment. *NB: the title of this question was edited in view of the emphasis by respondents on security and standards.*