Whenever Qubes is significantly affected by an XSA, a [Qubes Security Bulletin (QSB)](/security/bulletins/) is published, and a link to that QSB is added to the row for the associated XSA.
* For the purpose of this tracker, we do *not* classify mere [denial-of-service (DoS) attacks](https://en.wikipedia.org/wiki/Denial-of-service_attack) as affecting the *security* of Qubes OS.
* For simplicity, we use the present tense ("is affected") throughout this page, but this does **not** necessarily mean that up-to-date Qubes installations are *currently* affected by any particular XSA.
In fact, it is extremely unlikely that any up-to-date Qubes installations are vulnerable to any XSAs on this page, since patches are almost always published concurrently with QSBs.
* Embargoed XSAs are excluded from this tracker until they are publicly released, since the [Xen Security Policy](https://www.xenproject.org/security-policy.html) does not permit us to state whether Qubes is affected prior to the embargo date.
* Unused and withdrawn XSA numbers are included in the tracker for the sake of completeness, but they are excluded from the [Statistics](#statistics) section for the sake of accuracy.
