Safely open a list of links in Firefox
Rather than implementing this yourself, Python by default has webbrowser. This allows you to open one link in a; new tab, or new window. And so, to open all links in the list with the default web-browser you can:

import webbrowser

for link in links:
    webbrowser.open_new_tab(link)


Since you say you don't trust the source of these urls, you can make sure they are actually URLs, and check there is no shell injection going on. This question says how you could do that.

And so I personally would use:

import webbrowser

import rfc3987

def open_links(links):
    links = (
        link
        for link in links
        if rfc3987.match(link, rule='IRI') is not None
    )
    # Get default webbrowser, change if you want to force a specific browser
    browser = webbrowser.get()
    try:
        browser.open_new(next(links))
    except StopIteration:
        pass
    else:
        for link in links:
            browser.open_new_tab(link)