[sln] Update version to be in line with security hotfix release

This avoids "am I vulnerable to this?" confusion if running a :dev image or a -git package.

CHANGELOG.md

@@ -1,3 +1,16 @@
+## v2024.1-beta4.security1
+This is a security hotfix release. It's identical to v2024.1-beta4, except for the security mitigations listed below. Upgrading is strongly recommended for all server operators.
+
+### Backend
+- ActivityPub actor and note validation has been improved & now protects against cross-origin identifiers in more places, resolving a database pollution vulnerability
+- Cross-origin `url` properties on actor & note objects now get set to null before ingestion, resolving a clickjacking vulnerability
+- User resolution when processing incoming notes is now limited
+
+### Attribution
+This release was made possible by project contributors: Laura Hausmann
+
+Furthermore, I want to give special thanks to Hazel Koehler for the vulnerability disclosure.
+
 ## v2024.1-beta4
 This release contains lots of new features & bug fixes, including security fixes. Upgrading is strongly recommended for all server operators.
 

Directory.Build.props

@@ -27,7 +27,7 @@
     <!-- Version metadata -->
     <PropertyGroup>
         <VersionPrefix>2024.1</VersionPrefix>
-        <VersionSuffix>beta4</VersionSuffix>
+        <VersionSuffix>beta4.security1</VersionSuffix>
     </PropertyGroup>
 
     <ItemGroup>