Fix broken link to blast radius analysis documentation

Author: DebLanger

exposure-management/whats-new.md

@@ -26,6 +26,15 @@ Learn more about MSEM by reading the blogs, [here](https://techcommunity.microso
 
 ## September 2025
 
+### Blast radius analysis
+
+Blast radius analysis is an advanced graph visualization integrated into incident investigation experience. Built on the Microsoft Sentinel data lake and graph infrastructure, it generates an interactive graph showing possible propagation paths from the selected node to predefined critical targets scoped to the user’s permissions.
+
+> [!NOTE]
+> Blast radius analysis extends and replaces Attack path analysis.
+
+For more information, see [Blast radius analysis](https://learn.microsoft.com/en-us/defender-xdr/investigate-incidents?branch=release-preview-sentinel-graph#blast-radius-analysis)
+
 ### New predefined classifications
 
 The following predefined **Device** classification rules were added to the critical assets list: