In the company where I work (webhosting) our custoumers can choose the PHP version they want to use for their website.
However, I have just realized that all of the offered PHP versions are outdated (ie. PHP 5.4.38, 5.5.22 and 5.6.6 being offered to our clients - current versions are 5.4.43, 5.5.27 and 5.6.11). How dangerous is that to our customers? Is running those old versions pure madness or is it just a minor risk for our customers?
edit: There are no security updates applied, it is just PHP 5.4.38 from a few months ago.