Recently a Linux kernel vulnerability (CVE-2020-14386), which allows for memory corruption and possible privilege escalation, was announced [0].
Our security team began investigating and preparing our remediation strategy yesterday (September 3) at 22:00 UTC. As part of our remediation efforts, we will be restarting all App, Bastion, and Build instances in shared stacks today.
We will update this status page if any further action is required.
[0]
https://seclists.org/oss-sec/2020/q3/146