Hackers have begun to actively target WordPress sites running the OneTone theme in an effort to exploit a vulnerability that gives them the ability to read and write cookies as well as create backdoor admin accounts.
The vulnerability being exploited in the ongoing campaign is a cross-site scripting (XSS) bug in the OneTone WordPress theme created by the developer Magee WP which has not been updated since 2018.
The XSS vulnerability, which allows an attacker to inject malicious code into the the theme’s settings, was first discovered by NinTechNet’s Jerome Bruandet back in September of last year. Bruandet informed Magee WP as well as the WordPress team about the bug at the time, though the developer did not release a patch for the issue despite the warning.
This led the WordPress team to remove the listing for the free version of the theme from the official WordPress repository in October of last year. However, at the time of writing, just under 16,000 WordPress users still have the theme on their sites.
According to a new report from the cybersecurity firm Sucuri, hackers began actively exploiting the bug in OneTone earlier this month.
Malware researcher at the firm, Luke Leak explained that hackers are using the XSS bug to insert malicious code inside of OneTone theme’s settings. As the theme checks these settings before loading any page, the malicious code is executed on every page of a vulnerable site.
The code itself serves two functions as it redirects some of a vulnerable site’s users to a traffic distribution system hosted at ischeck.xyz while a second function enables the creation of backdoors. The malicious code even has the ability to recognize site admins as it looks for the presence of the WordPress admin toolbar at the top of a page.
Once a user with admin-level privileges is detected, the code then adds an admin account to a site’s WordPress dashboard (under the user name system) or creates an admin account-level cookie file on the server-side named Tho3faeK. These two backdoors grant an attacker access to the site even if their malicious XSS code is removed from OneTone’s settings or the vulnerability ends up being patched.
However, it looks like a patch to fix the OneTone vulnerability won’t be coming any time soon as Magee WP has not updated the theme since 2018. Therefore, WordPress users still running the theme should disable it to avoid falling victim to this latest hacking campaign.