Synology has released Update 1 for Disk Station Manager 5.2-5592. While there are only two documented fixes one of them is a security fix so the update should be applied as soon as possible.
Documented updates include:
Fixed an issue where applied settings could not be correctly displayed when changes were made at Group > Applications.
Upgraded OpenSSL to 1.0.1p to address a security vulnerability (CVE-2015-1793).
I successfully applied the update to Synology models DS212+, DS415+, DS1511+ and DS1815+.
While the browser interface for DSM is dedicated to the update and you can't do other tasks, the Disk Station does not do a full reboot so it takes less than two minutes to apply the update. Affected services will be stopped and started so users should still be warned. Drive shares became unavailable at the end of the update and had to be reconnected at the client Windows or Mac PC. Encrypted drive shares remained available and the encryption password did not have to be re-entered.