Dear webmasters, I just noticed a lot of my sites that are meant for SEO purpose are showing different cache than its original. http://www.rietionline.net/ for instance. If someone could enlighten what's causing it, that'd be truly appreciable. Thanks in advance.
This is cloaking, made for the purpose of linking to different resources. Your site is hacked. Try to look at your site through Google's Webmaster as Googlebot. You need to restore site from backup and install the latest version of WordPress.
Looks like it. I figured all those sites are hosted on same cheap hosting. So, the theory is upon updating the wordpress and plugins, it shall no longer be an issue?
If hacked from the outside, when you update WordPress and plugins should be no problems. Better probably remove all scripts and then again from scratch install the latest versions. Also need to see if htaccess, htaccess permissions and root directory permissions have not been changed. But if hacked through other sites from this hosting or through some vulnerability of hosting, then this is hard to defend, and then maybe have to change hosting provider. Maybe the details of hacking can be traced through host logs.