What is the KB number for the final XP Windows Update?
https://technet.microsoft.com/library/security/ms14-021 (kb2965111) seems to be the last.
I wasn'table to find any newer out-of-band updates for Windows XP.
Support for Windows XP ended on April 8, 2014.
Source What does it mean if Windows isn't supported?
Out-of-band fix for Internet Explorer zero-day flaw now available --
for XP, too.
That was fast: Microsoft today released an emergency patch for a
previously unknown Internet Explorer vulnerability revealed over the
weekend that was discovered being exploited by a cyber espionage group
out of China.
In a surprise twist, Microsoft included a patch for IE on Windows XP,
the older operating system it no longer supports as of last month.
Microsoft was under pressure for a quick fix to the flaw
(CVE-2014-1776), which came just after it ended support for Windows
XP, prompting advice from UK and US CERTs for users to consider using
alternative browsers until IE got its patch. The bug, a "critical"
memory corruption vulnerability, according to Microsoft, was spotted
being used in drive by web attacks. It affects IE versions 6, 7, 8, 9,
10, and 11, and basically allows an attacker to remotely run code on a
targeted machine.
Source Microsoft Issues Emergency Patch for IE, Covers XP
MS14-021 (Released out-of-band on May 1, 2014)
Security Update for Internet Explorer (2965111)
This security update resolves a publicly disclosed vulnerability in
Internet Explorer. The vulnerability could allow remote code execution
if a user views a specially crafted webpage using an affected version
of Internet Explorer. An attacker who successfully exploited this
vulnerability could gain the same user rights as the current user.
Users whose accounts are configured to have fewer user rights on the
system could be less impacted than users who operate with
administrative user rights.
Source Microsoft Security Bulletin Summary for May 2014 (CVE-2014-1776)