How can I install a Firefox addon via nsis installer?
When I call Firefox with the .xpi extension it doesn't work and xpi extensions are not associated with Firefox either.
If I drop it to "C:\Program Files\Mozilla Firefox\extensions" then it tries to install every single time a user opened the Firefox. Never deletes the original xpi (potentially due to the Vista UAC)
By using the correct command line parameter :)
firefox -install-global-extension c:\extension.xpi
Refer documentation