Short container image tags (without "jdk" in them) such as jenkins/jenkins:2.426.1 are now using Java 17. If you need to continue using Java 11, use tags like jenkins/jenkins:2.426.1-jdk11. The Windows container images of this release switch from a windowsservercore-1809 Temurin base image to a windowsservercore-ltsc2019 Microsoft base image. Note also that a proper set of tags is now published for these Windows images and they include "ltsc2019" instead of only "2019".
Changes since 2.426:
Show form validation results for form elements that are initially hidden.
Remove previous form validation errors when the form validation is updated with new content (regression in 2.355).
(issue 71252, issue 70793)
Fix multibranch Pipeline Add source and other uses that mix inputs and buttons (regression in 2.422).
(issue 72170)
Add sleep call when -noReconnect is not specified for Kubernetes agents.
(Remoting PR 675)
Show the description of boolean build parameter values on the Parameters view (regression in 2.179).
(issue 72179)
Allow clouds to be reordered.
This was previously possible, but disappeared when the cloud management was moved to a separate page (regression in 2.403).
(issue 72020)
Update SnakeYAML plugin to 2.2 to silence security scanners.
(issue 70994)
Automate the display of an administrative monitor when approaching Java end of life (EOL) dates.
(pull 8526)
Remove System V initialization scripts from RPM based installers.
The System V initialization scripts were replaced in March 2022 with systemd initialization.
RPM users with a custom log directory no longer have a logrotate(8) configuration out-of-the-box.
(pull 409 (packaging), Linux install packages migrated from System V init to systemd)
Make tab panes accessible via keyboard.
(issue 71496)
Add allow-same-origin to the sandbox ContentSecurityPolicy directive of workspace and artifact browsers if the Resource Root URL feature is not used.
Allow requests to resources like stylesheets and images, even if a reverse proxy prohibits cross-site requests.
(issue 71366)
Message no longer appears twice when the agentLog option is used.
(issue 38520)
Hide administrative monitors icons/popup in the header of Manage Jenkins, as they're shown directly on the page.
(issue 71848)
Fix link to job in the message informing administrators of trigger computations that run for an unusually long time.
(issue 71833)
Use standard size node icon even with long node names.
(pull 8089)
Add the X-Content-Type-Options HTTP header to the response from the agent listener.
Silence security scanners that incorrectly report an issue when the HTTP header is missing.
(issue 71186)
Only disable the plugin manager "install" button if no plugins are selected.
(issue 71698)
Estimate project duration accurately in more cases.
(pull 8233)