50,000 sites hit by MailPoet WordPress plug-in security flaw

Users of the popular MailPoet WordPress plug-in are being urged to update it, following the discovery of a vulnerability that has so far led to 50,000 websites becoming compromised.

The newsletter plugin contains a security vulnerability, which was first flagged by security researchers at the start of July, that allows hackers to remotely upload files to a website without obtaining authentication first.

A new version of MailPoet was released on the same day the researchers published a blog post on it, but it seems news of its arrival has not reached all users, as many are still using unpatched versions.

To date, the plug-in has been downloaded around 1.7 million times and, when the original blog post was published, it was unclear if the vulnerability had been exploited.

Now, the same researchers from security firm Sucuri have confirmed that thousands of Wordpress websites have been attacked, with hackers seizing on the MailPoet vulnerability to inject malware into them.

The malicious software has been found to corrupt numerous WordPress files, resulting in PHP error messages appearing on peoples' sites.

However, it's not just websites that have the MailPoet extension installed that are being affected, the researchers have warned.

"The MailPoet vulnerability is the entry point, it doesn't mean your website has to have it enabled or that you have it on your website; if it resides on the server, in a neighbouring website, it can still affect your website," the blog post states.

Those who do have the plug-in installed are being urged to upgrade it to the latest version now to prevent it from spreading further.