The Xen Project has published Xen Security Advisories 264, 265 and 266 (XSA-264, XSA-265, and XSA-266, respectively). These XSAs do not affect the security of Qubes OS, and no user action is necessary.

These XSAs have been added to the XSA Tracker:

https://www.qubes-os.org/security/xsa/#264

https://www.qubes-os.org/security/xsa/#265

https://www.qubes-os.org/security/xsa/#266