Jetpack version 2.9.3 contains a critical security update, and you should update your site and any you help manage as soon as possible. You can update through your dashboard, or download Jetpack manually here.
During an internal security audit, we found a bug that allows an attacker to bypass a site’s access controls and publish posts. This vulnerability could be combined with other attacks to escalate access. This bug has existed since Jetpack 1.9, released in October 2012.
Fortunately, we have no evidence of this being used in the wild. However, now that this update is public, it’s just a matter of time before exploits occur. To avoid a breach, you should update your site as soon as possible. (The vulnerability has been disclosed on the MITRE Common Vulnerabilities and Exposures system as CVE-2014-0173.)
This is a bad bug, and Jetpack is one of the most widely used plugins in the WordPress world. We have been working closely with the WordPress security team, which has pushed updates to every version of the plugin since 1.9 through core’s auto-update system. We have also coordinated with a number of hosts and network providers to install network-wide blocks to mitigate the impact of this vulnerability, but the only sure fix is updating the plugin.
Over the next few hours, we will reach out to individuals whose sites are still running an insecure version. Sites that don’t update may be disconnected from the Jetpack service for their own security, and will be able to reconnect as soon as their version of Jetpack is updated.
If you host a large number of Jetpack-powered blogs, please leave your contact information in the comments so we can be in touch in the future. We have prepared and shipped point releases for all eleven vulnerable branches of the Jetpack codebase: 1.9.4, 2.0.6, 2.1.4, 2.2.7, 2.3.7, 2.4.4, 2.5.2, 2.6.3, 2.7.2, 2.8.2, and 2.9.3. If you can force these upgrades for your hosted users, it will prevent their sites from being compromised.
Finding and fixing bugs is a key part of software development. I can’t promise there will never be another issue like this, but I can promise that when a problem is found we will do everything in our power to protect as many people as possible, as quickly as possible. We care deeply about each and every WordPress user.