WordPress 4.2 was released yesterday. This version adds some new features and improves others. This is not a security-related update.
Updating to version 4.2 also seems to trigger several theme updates. On one of my sites, which uses a Twenty Eleven child theme, an update to the parent Twenty Eleven theme caused the site to stop working completely. I was able to resurrect the site by installing the Twenty Eleven theme again manually. Update: apparently one of the download servers had an incomplete copy of the theme. This problem has been resolved.
Confusingly, WordPress 4.1.3 was also released yesterday. Because it was released so soon after 4.1.2, it’s safe to assume that it contains more security fixes. However, details are sketchy at this point. There was no formal announcement of the release. The WordPress Codex entry for version 4.1.3 says ‘Fix database writes for esoteric character sets, broken in the WordPress 4.1.2 security release.’
WordPress sites configured for auto-updates will update themselves to version 4.1.3 over the next few days. Depending on the auto-update settings, WordPress sites may also update themselves to version 4.2, bypassing 4.1.3. This shouldn’t be a problem, since it’s safe to assume that any fixes in 4.1.3 are also in 4.2.
Your best bet at this point is to update your WordPress sites manually to version 4.1.3. Then start testing version 4.2; once you’re sure it’s not going to break anything, upgrade your production sites.
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