When it comes to the security of WordPress plugins what other security companies generally do is to add protection against vulnerabilities after they have already been widely exploited, which obviously won’t produce great results since there is a good chance the websites using their service have already been hacked by the time they do that. One of the ways we keep ahead of that is to monitor the closure of the 1,000 most popular WordPress plugins in the Plugin Directory, since that closure can be due to a security issue and even if it is not, we have found the plugins being closed often contain security vulnerabilities, and as was the case with one less than two weeks ago, ones likely to be exploited. Hackers seem to be doing that type of monitoring as well. Through that we found that the plugin Visual CSS Style Editor, which has 30,000+ active installs and was closed yesterday, has two vulnerabilities that when combined lead to a type of vulnerability hackers would be likely to exploit.

When we started to do a quick check of the security of the plugin after we were notified by our monitoring that it was closed, we found that were multiple basic security failures. For example, our Plugin Security Checker, which is an automated tool anyone can use to check plugins for possible security issues, correctly identified the possibility of a reflected cross-site scripting (XSS) vulnerability. But that isn’t a serious issue, so we went to look if there was something more serious that we should be warning our customers about instead. We found something that fit the bill, but there could be other issues as well. [Read more]