Posted by Chris Evans and Drew Hintz, Security Engineers We recently discovered that attackers are actively targeting a previously unknown and unpatched vulnerability in software belonging to another company. This isn’t an isolated incident -- on a semi-regular basis, Google security researchers uncover real-world exploitation of publicly unknown (“zero-day”) vulnerabilities. We always report these cases to the affected vendor immediately, and we work closely with them to drive the issue to resolution. Over the years, we’ve reported dozens of actively exploited zero-day vulnerabilities to affected vendors, including XML parsing vulnerabilities, universal cross-site scripting bugs, and targeted web application attacks. Often, we find that zero-day vulnerabilities are used to target a limited subset of people. In many cases, this targeting actually makes the attack more serious than a broader attack, and more urgent to resolve quickly. Political activists are frequent targets, and the consequences of being compromised can have real safety implications in parts of the world. Our standing recommendation is that companies should fix critical vulnerabilities within 60 days -- or, if a fix is not possible, they should notify the public about the risk and offer workarounds. We encourage researchers to publish their findings if reported issues will take longer to patch. Based on our experience, however, we believe that more urgent action -- within 7 days -- is appropriate for critical vulnerabilities under active exploitation. The reason for this special designation is that each day an actively exploited vulnerability remains undisclosed to the public and unpatched, more computers will be compromised. Seven days is an aggressive timeline and may be too short for some vendors to update their products, but it should be enough time to publish advice about possible mitigations, such as temporarily disabling a service, restricting access, or contacting the vendor for more information. As a result, after 7 days have elapsed without a patch or advisory, we will support researchers making details available so that users can take steps to protect themselves. By holding ourselves to the same standard, we hope to improve both the state of web security and the coordination of vulnerability management. 