YUI End of Life (EOL) Dates & Support Timeline
Complete end-of-life dates, support windows, and security status for all YUI versions. Data sourced from endoflife.date and official vendor documentation. Updated at every deploy.
| Version | Latest Release | Release Date | EOL Date | Days | Status |
|---|---|---|---|---|---|
| 3 | 3.18.1 | Sep 29, 2009 | Aug 29, 2014 | 4331 days past EOL | EOL |
YUI lifecycle status — the real story
YUI is the textbook case of an explicit corporate end of life: Yahoo announced the end of active YUI development on August 29, 2014, citing the rise of Node.js, package managers, and evolving JavaScript standards. The final release, 3.18.1, shipped in October 2014 — meaning every YUI deployment has now gone over a decade without patches.
YUI once ran substantial parts of the commercial web, and remnants survive in long-lived enterprise applications and CMS themes. Multiple publicly documented XSS vulnerabilities exist in YUI 2 and early YUI 3 components, and no fix will ever be issued.
Any live YUI dependency belongs at the top of a legacy remediation list — it is one of the few libraries where "unsupported" is not an inference but an eleven-year-old official announcement.
What does YUI end of life mean for your organization?
When a version of YUI reaches end of life, the maintainers stop issuing security patches. Vulnerabilities discovered after this date are publicly disclosed on the National Vulnerability Database, exploit code appears on GitHub, and your systems remain permanently exposed.
The CVE blind spot: Most vulnerability scanners check for known CVEs but do not flag the accumulation of unpatched vulnerabilities in EOL software. With a zero-day, nobody knows about the vulnerability. With EOL software, the vulnerability is public — listed, rated, and often weaponized — but no patch will ever exist. This is the most dangerous gap in enterprise security posture.
Organizations running EOL YUI should treat it as a vulnerability class in their risk register, apply compensating controls (network segmentation, enhanced monitoring, access restriction), and prioritize migration to a supported version.
Extended Support Options
If you cannot migrate immediately, extended support vendors provide continued security patches for EOL YUI versions. This is a bridge, not a permanent solution — plan your migration in parallel.
We work with vetted extended support vendors. Tell us what you need and we'll connect you with the right provider.
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