Self-hosted installations of WordPress are at risk of attack following the disclosure of a vulnerability in a widely used plugin for the blogging software-cum-website CMS.
The vulnerable TimThumb plugin is used by many blogs to easily resize images. However a zero-day vulnerability in the Webshot function of TimThumb (2.8.13 - the latest version) creates a means to inject hostile code – or worse – onto vulnerable sites.
Researchers at infosec haus Sucuri warn that attackers can “create, remove and modify any files" on vulnerable systems. Bloggers are advised to disable the vulnerable Webshot function as a workaround.
TimThumb’s Webshot option is disabled by default, according to veteran security expert Graham Cluley, a factor which he says limits the vuln's potential to cause harm. The buggy TimThumb library code can be installed by a third-party theme or plugin, so it might be running on WordPress sites without the owners necessarily being aware that it's there.
The vulnerability was disclosed through a Full Disclosure mailing list without notifying TimThumb's developers beforehand. The developers were able to act quickly and released TimThumb version 2.8.14, which resolves the vulnerability.
TimThumb has been used to commandeer thousands of WordPress blogs in the past, and it's a well known hacker target in general for RFI (Remote File Inclusion) attacks, among other forms of malfeasance. Over recent months, in particular, cybercrooks have taken to abusing vulnerable WordPress installations to either run denial of service attacks or to act as command and control nodes for botnets. ®