(2015/02/04)
Fixed Issues
Implemented fixes related to the GHOST vulnerability (CVE-2015-0235).
Upgraded PHP to 5.5.21 to address multiple vulnerabilities (CVE-2015-0231, CVE-2014-9427, and CVE-2015-0232).

Version : 5.1-5022 Update 3

(2015/03/02)
Fixed Issues

Fixed a security vulnerability related to SAMBA (CVE-2015-0240).

Version : 5.2-5532 Update 1

(2015/03/21)
Fixed Issues
Fixed an issue where it could take a long time for the system to respond when opening files via the SMB protocol.
Fixed an issue where some services could not function normally when a fixed IP address is assigned to an unused LAN port.
Fixed an issue where backup tasks would fail when upgrading from DSM 5.0.
Fixed an issue where the usage of memory could become abnormally high when performing backup tasks.


Version : 5.1-5022 Update 4

(2015/03/21)
Fixed Issues
Upgraded OpenSSL to 1.0.1m to address multiple vulnerabilities (CVE-2015-0204, CVE-2015-0286, CVE-2015-0287, CVE-2015-0289, CVE-2015-0292, CVE-2015-0293, CVE-2015-0209, and CVE-2015-0288).

Version : 5.1-5022 Update 5

(2015/04/23)
Fixed Issues
Fixed a vulnerability that could allow unauthorized access to the shared folders via SMB protocol.

DSM Version : 5.2-5565

(2015/05/12)
Compatibility and Installation
DSM 5.2 can only be installed on Synology products running DSM 5.0 or above. Before starting, please log in to DSM and go to DSM Update to install the latest DSM.
Some features have specific hardware requirements and are only available on certain Synology NAS products.
Important Notes
DSM 5.2 is the last supported major DSM version for all 10-series models.
An issue of data consistency caused by SSD TRIM is not resolved yet; as a result, SSD TRIM is currently disabled in DSM 5.2.
DSM 5.2 is the last DSM version to support Time Backup as an add-on application in Package Center. Time Backup features will be fully merged into the built-in Backup package in future releases. Existing Time Backup users will not be affected.
Sharing via Facebook and Google+ will no longer be supported starting from DSM 5.2.
What’s New in DSM 5.2
Single Sign-On
You can register multiple DSM and access them using one set of credentials. After initial login, linked DSM accounts will automatically log in to avoid credential re-authentication.
Windows File Sharing
Added SMB3 and end-to end data encryption support.
Backup and Replication
Added support for file-level restoration with File Version Browser in multi-version backup tasks.
You can set up backup rotation to recycle old backup versions automatically in multi-version backup tasks.
Added data transfer encryption support for multi-version backup.
Added support for Amazon S3 China Region as a backup destination.
iSCSI LUN Snapshots
You can take iSCSI snapshots more frequently, up to every five minutes.
You can set the snapshot retention policy to retain a specific number of versions for hourly, daily, weekly, monthly, and yearly snapshots.
Link Aggregation
Added support for two new modes when creating a bond interface: Adaptive Load Balancing and Balance XOR.
SSD Cache
SSD cache now has a smaller memory footprint, consuming 90% less memory than DSM 5.1 for newly created SSD caches.
File Station
You can manage and transfer files to popular public cloud services such as Dropbox, Box, Google Drive, and OneDrive.
The built-in photo viewer now supports full-screen mode.
You can drag and drop files between two browsers.
You can set the number of times a shared link can be accessed.
Added playlist support for the built-in audio player.
You can use the built-in mail client to send shared links.
QuickConnect
Enhanced stability.
DSM will automatically add port forwarding rules required by QuickConnect services on your compatible UPnP router, saving your time on network configuration.
DSM log-in page
You can add welcome messages to deliver information to users before they log in to the system.
DSM Help
You can reach online resources such as FAQ and compatibility lists in DSM Help now.
One more tutorial about how to back up data from your computer is added in the section of Get started with DSM.
Misc
You can customize the security level of SSH connections by selecting which encryption algorithm(s) to use.
Added more flexible port forwarding rules, including assigning random port numbers, and customized port settings.
You can set usage quotas for different groups. The group usage quota is automatically applied when a user is added to the group.
What’s New in Packages
Single Sign-On Package
Based on the OAuth2 standard, SSO Server package turns Synology NAS into a SSO server that allows developers to register their web applications to the server and utilize the single sign-on feature. This increases daily productivity by saving time spent on re-authentication.
Docker
Docker is a lightweight virtualization application that gives you the ability to run thousands of containers created by developers from all over the world on DSM. The hugely popular built-in image repository, Docker Hub, allows you to find shared applications from other talented developers.
A step-by-step tutorial is introduced to guide you through the basic container creation.
Note Station
Added to-do list feature. You can add tasks to notes or add them independently to the to-do list.
Manage tasks by specifying a priority, due date, and reminder.
Synology Web Clipper is now available on the Chrome Web Store. You can clip web content directly to Note Station.
Export notebooks to a nsx file for backup or for importing to another Synology NAS.
Export individual notes as HTML files so that users without Note Station can read them.
You can archive seldomly used notebooks so that they will not be displayed in the notebook section or in search results.
Enhanced Note Station file structure. A three-tier structure (Shelf, Notebook, and Note) provides greater flexibility for organizing Note Station.
You can display notes in presentation mode.
You can create new notes in a joined notebook if you were given modify permissions.
You can share notes via the built-in DSM email application.
You can change the default notebook.
You can adjust the default note font size.
Import notes from YinXiangBiJi.
Better note version conflict handling.
Todo badge number on Desktop icon.
Cloud Station
Added support for low-latency smart polling.
You can assign different historic version numbers for each shared folder.
Enhanced general performance.
Added support for native renaming operation.
Administrators can enable/disable Cloud Station directly from Package Center.
Added support for File Station Recycle Bin.
Files greater than 10GB can be synced.
Updated PC client for Windows, Mac and Linux:
Added a quick setup wizard.
Added a search feature to automatically find all Synology NAS in the local area network.
Added a system tray menu in graphic user interface.
You can right-click to stop or resume syncing for specific subfolders.
You can right-click a synced folder to generate a folder sharing link.
You can right-click any file on your computer to copy it to the Cloud Station folder.
Added a client-side sync log.
Cloud Sync
Added unidirectional sync from NAS to public cloud and from public cloud to NAS.
You can encrypt and compress data sent to public cloud storage.
Added support for Amazon S3 compatible public cloud service providers.
Added support for WebDAV public cloud service providers.
Added support for Amazon Cloud Drive.
Added support for Megafon Disk.
Added support for native renaming operation (support level differs with public cloud storage API).
You can customize both task name and polling period.
You can sync files as large as 10GB with OneDrive.
Added support for File Station Recycle Bin.
Mail Server
Added attachment filter to block specific file extensions.
You can receive real-time notifications regarding daily quota status.
Added support for SPF/DKIM and DMARC sender validation.
Added customized auto-reply and content setting features.
Daily quotas can be set by user.
Glacier Backup
Enhanced to handle Amazon server-side speed limit.
Enhanced general performance.
Video Station
You can use hotkeys to fast forward, rewind, and adjust the volume during video playback.
Subtitle files can now be located anywhere on your Synology NAS and no longer need to match the filename of your video files. Simply select them using the built-in chooser in Video Station during playback.
More code-pages supported to correctly recognize subtitles in different languages.
You can set a timing offset to sync subtitles with video playback.
You can customize video posters by selecting an image from your Synology NAS.
Use the shortcut on the library to quickly add video folders.
You can delete videos directly from Video Station
Supported right-click context menu to access useful functions more quickly.
Audio Station
Added support for indexing CUE sheet files to display all indexed audio tracks, and the song information of an undivided album file for management (requires DSM 5.2).
Added support of transcoding FLAC/APE, ALAC/AAC, OGG, AIFF formats for DLNA players.
Photo Station
A brand-new design that gives Photo Station mobile a refreshed look-and-feel. The update includes two major improvements: watching videos and linking directly to details page of a photo.
You can select specific albums when creating a smart album.
More EXIF information is displayed in the lightbox page, and can also be added as conditions when creating smart albums.
Download Station
Previews for photos and videos are available for torrent downloads.
Added support for HTTP downloads with multiple connections.
Media Server
Resumed video transcoding support (This feature is supported by select models. Please go here for detailed information).
Redmine
Redmine is a flexible project management web application. It has numerous features and can be run on Synology NAS via Docker.
GitLab
GitLab is a web-based Git repository manager with wiki and issue tracking features. It has numerous features and can be run on Synology NAS via Docker.
LXQt
LXQt is a desktop utility built on QT with partial Razor-qt and LXDE components. It comes with a basic graphical user interface which gives users the ability to leverage certain operating system features, such as web browsing. It has numerous features and can be run on Synology NAS via Docker.
SpreeCommerce
SpreeCommerce is a full-featured storefront tool built on common standards so you do not have to compromise speed to market, efficiency, or innovation. You can also easily leverage the advantages of modular design to configure, supplement, or replace the functionalities you need. It has numerous features and can be run on Synology NAS via Docker.
Discource
Discourse is a forum application software with a focus on user experience by introducing infinite scrolling, live updates, drag and drop attachments and more. It has numerous features and can be run on Synology NAS via Docker.
MantisBT
MantisBT is an open source, web-based issue tracker and project management tool with a focus on simplicity and flexibility. Users are able to get started quickly and manage their projects effectively, making collaboration with team members and clients easy and professional.
LimeSurvey
LimeSurvey is a powerful survey creation tool that help you easily create and publish intuitive and question-and-answer surveys and collect responses without the requirement of technical background. LimeSurvey also provides graphical analysis of the result for you to quickly find the information from the statistics. You also have the full control of whom to access the survey, either publish the survey publicly or limit only the users with the "once-only" token.
CMS
Enhanced general performance.
Bug fixes and usability enhancements.