I find it worrying that people set up a Joomla site and once running they seem to assume that it will continue to run safely forever! Every day in this forum we see people using Joomla and VirtueMart versions with known critical security issues, just waiting for a hacker to come along. That is the last thing you want on a working eCommerce website. You could lose your reputation, as well as lose sales and possibly be fined for breaches of data security. Some Joomla/VM sites simply stop working after 3-4 years in use, having never been updated, commonly this is caused by the PHP version on the host server being updated.
No Joomla version before 3.9.28 is officially secure for use on a live website. No website using Joomla versions 1.5.x or 2.5.x is secure.All previous versions have bugs & security issues some of which are critical, and many sites with earlier versions have been hacked. If you have not seen hacked site issues yourself, just browse through the Joomla security board to see a whole lot of people with problem sites.
https://forum.joomla.org/viewforum.php?f=714 See
http://developer.joomla.org/security-centre.html for latest security issues.
All VirtueMart versions before 3.8.6 are insecure and cannot be recommended for use on live sites.
Check for latest VM release versions on http://dev.virtuemart.net/projects/virtuemart/files Always test updates on a backup copy of your site. Commercial template users may need to update/edit their template overrides if they were originally for a much older version of VirtueMart.It is easy to keep up with the security status of Joomla - just subscribe to
http://feeds.joomla.org/JoomlaSecurityNewsFor security and new reports of VirtueMart subscribe to
http://feeds2.feedburner.com/VirtuemartNews or regularly visit
http://virtuemart.net/news/list-all-news where you can also sign up to have the VM news items emailed to you when released.
For vulnerabilities in Joomla extensions subscribe to this feed:
http://feeds.joomla.org/JoomlaSecurityVulnerableExtensions It is always a good idea to update to the latest current version when a security warning is issued.
BUT always test updates on a backup copy of your site, never the live version.Not using a secure version can lead to a failure to pass a PCI scan and now possibly a large fine under EU GDPR regulations.