Fix: copilot feedback

Author: BornToBeRoot

Source/NETworkManager.Tests/Utilities/RegexHelperTests.cs

@@ -80,7 +80,14 @@ public void HostnameOrDomain(string input, bool isMatch)
     [Theory]
     [InlineData("borntoberoot.net", true)]
     [InlineData("local.example.com", true)]
+    [InlineData("server-01.example.com", true)]
+    [InlineData("example.com.", true)]
     [InlineData("example", false)]
+    [InlineData("example.c", false)]
+    // A hyphen at the start or end of a label, like hostnames
+    [InlineData("server.-bad-.com", false)]
+    [InlineData("-example.com", false)]
+    [InlineData("example-.com", false)]
     public void Domain(string input, bool isMatch)
     {
         Assert.Equal(isMatch, Regex.IsMatch(input, RegexHelper.DomainRegex));

Source/NETworkManager.Utilities/RegexHelper.cs

@@ -170,10 +170,11 @@ public static partial class RegexHelper
     // Match a hostname with subnetmask like server-01.example.com/255.255.255.0
     public const string HostnameOrDomainWithSubnetmaskRegex = $@"^{HostnameOrDomainValues}\/{SubnetmaskValues}$";
 
-    // Match a domain local.example.com (labels without nested quantifiers, which backtrack exponentially for an invalid
-    // input with many labels)
+    // Match a domain local.example.com: labels like a hostname (see HostnameLabelValues, no hyphen at the start or end)
+    // and a top-level domain of letters. Without nested quantifiers, which backtrack exponentially for an invalid input
+    // with many labels.
     public const string DomainRegex =
-        @"^(?=.{1,255}$)[a-zA-Z0-9\-_]{1,63}(\.[a-zA-Z0-9\-_]{1,63})*\.[a-zA-Z]{2,63}\.?$";
+        $@"^(?=.{{1,255}}$)(?:{HostnameLabelValues}\.)+[a-zA-Z]{{2,63}}\.?$";
 
     // Private port values (1-65535, without leading zeros)
     private const string PortValues =

Website/docs/changelog/next-release.md

@@ -194,7 +194,7 @@ Release date: **xx.xx.2026**
 
 **Input validation**
 
-- Fixed host names being accepted with a hyphen at the start or end of a label other than the first (e.g. `server.-bad-.com`) and with only digits (e.g. `10.0.0.` or `192.168.1`, which are an incomplete IPv4 address). IPv4 addresses are still accepted in all host fields, now checked explicitly in the **Remote Desktop** host field. [#3646](https://github.com/BornToBeRoot/NETworkManager/pull/3646)
+- Fixed host names being accepted with a hyphen at the start or end of a label other than the first (e.g. `server.-bad-.com`) and with only digits (e.g. `10.0.0.` or `192.168.1`, which are an incomplete IPv4 address). The same applies to the domain in **Whois**. IPv4 addresses are still accepted in all host fields, now checked explicitly in the **Remote Desktop** host field. [#3646](https://github.com/BornToBeRoot/NETworkManager/pull/3646)
 - Fixed MAC addresses and their first 3 bytes (**Wake on LAN**, **Lookup** > **OUI**, profiles) being accepted with any character instead of a dot in the format `0000.0000.0000` (e.g. `0011 2233 4455`). [#3646](https://github.com/BornToBeRoot/NETworkManager/pull/3646)
 - Fixed IPv6 subnets in the **Subnet Calculator** being accepted with a leading `s` (e.g. `sss2001:db8::/32`) and rejected with an embedded IPv4 address (e.g. `::ffff:192.168.0.1/96`). [#3646](https://github.com/BornToBeRoot/NETworkManager/pull/3646)
 - Fixed the port of the **Remote Desktop** host field (`host:port`) being accepted empty or as `0`. [#3646](https://github.com/BornToBeRoot/NETworkManager/pull/3646)