WordPress versions 5.1 and earlier are affected by the following bugs which are fixed in the
updated 5.1.1 version.
Some other highlights of this release include:
To Browser the full list of changes on Trac please click the link below
https://core.trac.wordpress.org/query?status=closed&resolution=fixed&milestone=5.1.1&order=priority
The WordPress 5.1.1 was a short-cycle maintenance release, the 5.1.2 version is expected to follow a similar precedence within two weeks.
Reference
https://www.us-cert.gov/ncas/current-activity/2019/03/14/WordPress-Releases-Security-Update