[sid0]

It's not a question of Firefox allowing this -- if you run any program on your computer it'll have access to your data (and hence to your Firefox profile), and one of the principles behind Firefox is extensibility.

[aboodman]

Chrome has taken the same approach Firefox did:

We can't prevent this from happening so we try to provide a good way for other software to do it, so they don't do it in terrible ways:

http://code.google.com/chrome/extensions/external_extensions...