Dear
jcmm, just tried myself (Firefox+paypal), and I can proceed 'till the last steps and also login into my paypal account.
Are you sure it's Firefox and/or paypal to tell you that the site is insecure, and not your antivirus/firewall software?
Are you sure you tried to buy BS.Player Pro from the official page (
http://www.bsplayer.com/bsplayer-english/purchase.html)?
I reported the purchase page link in non linkable way to let you verify that the link is the right one!
Beware from the scam sites, and if you verify that you tried to but BS.Player Pro from an unauthorized site, please, report it here as soon as you can with all the details related to that site.
Thank you very much