[luuvasara]

What

The default installation goes from Virtual DSM 7.2.2-72806 to 7.4.1-90080, the latest full installer Synology publishes for VirtualDSM. The README sentence about the default version is updated to match.

Why

The default was last changed in #815 (2024-09-11). Since then Synology has published full VirtualDSM installers for 7.3, 7.3.2, 7.4 and 7.4.1. I couldn't find any reason in the issues, PRs or docs for staying on 7.2.2. Users already run 7.3 and newer by upgrading inside DSM, e.g. #1050 and #1117.

New installs currently start on a build that misses fixes Synology has since shipped. One example is Synology-SA-26:13, which covers remote CVEs rated CVSS 9.8 and is only fixed in 7.2.2-72806-9 or later, or 7.4-90075 or later. A fresh 7.2.2 install stays exposed until the user runs DSM's updater. 7.4.1 also brings newer bundled components, e.g. PHP 8.1.9 → 8.1.32 and OpenSSL 3.0.9 → 3.0.19.

Existing installations are not affected. Their system image is found through dsm.ver before the default URL is used, and setting URL still selects any other version.

Testing

• Both mirrors serve the file: global.synologydownload.com and cndl.synology.cn each return HTTP 200 with 381442836 bytes.
• I built this branch and started it with an empty /storage and no URL. It downloaded DSM_VirtualDSM_90080.pat, installed it and booted. The healthcheck reported healthy and port 5000 showed "Welcome to DSM 7.4".