A zero-day vulnerability with critical severity has been discovered in Google Chrome, and has been patched in an emergency Chrome 116 security update, after in-the-wild exploitation was observed.

The vulnerability was reported as “a heap buffer overflow in WebP.” Heap buffer overflows occur when an application writes more data for a memory buffer than what the buffer can hold — this can cause an application to crash, leading to the possibility of arbitrary code execution. WebP, meanwhile, is an image format “that provides superior lossless and lossy compression for images on the Web,” which means that Web developers are able to use it to create smaller and richer images vs. JPEG- and PNG-formatted images. In turn, that allows the Web to run faster. WebP images are supported by most modern browsers, such as Chrome, Firefox, Safari, Edge, and Opera.

The issue was reported by Apple Security Engineering and Architecture (SEAR) and spyware watchdog The Citizen Lab on Sept. 6, and Google reported in its advisory this week that it is aware that an exploit for the bug — tracked as CVE-2023-4863 — exists in the wild. It did not provide details on the nature of the active campaigns.