The Xen Project has published Xen Security Advisories 276, 277, and 279 (XSA-276, XSA-277, and XSA-279, 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/#276

https://www.qubes-os.org/security/xsa/#277

https://www.qubes-os.org/security/xsa/#279