I want to set up an instance of Firefox to be used to access a strictly limited "white list" of websites (my bank's, my credit cards', etc.).
How can I harden such an instance of Firefox to reduce (eliminate?) the possibility of straying outside of the white listed sites?
Since this instance of FF will not be used for casual browsing, it is OK if it is modified in a way that makes it more secure at the expense of "ease of browsing."
Also, here, I am primarily interested in built-in config settings, as opposed to third-party add-ons (aka extensions).
(I don't mind learning about add-ons that may be useful to harden Firefox for the use described above1, but this information would be only "for future reference", until I learn how to inspect an add-on to determine that it is neither malicious nor vulnerable.)