Synology released DSM 5.2-5592 Update 4 back on Monday. The update includes some very important updates. If you use the Antivirus Essentials package you may have found it detected a Synology system file as infected. This update restores that file in the event it was deleted. I'd recommend updating the AntiVirus Essentials package first since it fixes the false detection although Synology may have dealt with this possibility (that is, having the newly replaced file seen as a virus). Other fixes are security related or fix a problem with system recovery.
The entire fix list is:
- Restored the mandatory file (/usr/syno/bin/zip) that has been removed due to Antivirus Essential's false-positive detection.
- Upgraded Apache HTTP Server to 2.2.31 to address one security vulnerability (CVE-2015-3183).
- Upgraded PHP to 5.5.28 to address two security vulnerabilities (CVE-2015-5589 and CVE-2015-5590).
- Fixed two security vulnerabilities to prevent cross-site scripting (XSS) attacks.
- Fixed a security vulnerability of PCRE library (ASA-201508-11).
- Fixed an issue where DSM cannot be updated after system recovery on certain models (DS2415+, DS1815+, DS1515+, RS815RP+, RS815+, DS415+).
Considering the fixes included with this update you should make time to apply it as soon as possible. The update will reboot the NAS. I successfully applied the update to a DS1815+, DS415+, DS212+ and a DS1511+ without a problem.