[Security] 9.0.4 release notes (#2080)

Resolves #1926: adds the
9.0.4 Security and Elastic Defend release notes.

Previews:
* [Elastic Security release
notes](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/2080/release-notes/elastic-security/)
* [Known
issues](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/2080/release-notes/elastic-security/known-issues)

Author: natasha-moore-elastic

release-notes/elastic-security/index.md

@@ -27,6 +27,22 @@ To check for security updates, go to [Security announcements for the Elastic sta
 
 % *
 
+## 9.0.4 [elastic-security-9.0.4-release-notes]
+
+### Features and enhancements [elastic-security-9.0.4-features-enhancements]
+* Improves logging of fatal exceptions in {{elastic-defend}}.
+
+### Fixes [elastic-security-9.0.4-fixes]
+* Fixes differences between risk scoring preview and persisted risk scores [#226456]({{kib-pull}}226456).
+* Updates a placeholder and validation message in the **Related Integrations** section of the rule upgrade flyout [#225775]({{kib-pull}}225775).
+* Excludes {{ml}} rules from installation and upgrade checks for users with Basic or Essentials licenses [#224676]({{kib-pull}}224676).
+* Allows using days as a time unit in rule schedules, fixing an issue where durations normalized to days were incorrectly displayed as 0 seconds [#224083]({{kib-pull}}224083).
+* Strips `originId` from connectors before rule import to ensure correct ID regeneration and prevent errors when migrating connector references on rules [#223454]({{kib-pull}}223454).
+* Fixes an issue that prevented the AI Assistant Knowledge Base settings UI from displaying [#225033]({{kib-pull}}225033).
+* Fixes a bug in {{elastic-defend}} where Linux network events would fail to load if IPv6 is not supported by the system.
+* Fixes an issue in {{elastic-defend}} that may result in bugchecks (BSODs) on Windows systems with a very high volume of network connections. This issue has only been observed on Windows Server.
+* Fixes an issue where {{elastic-defend}} may incorrectly set the artifact channel in policy responses, and adds `manifest_type` to policy responses.
+
 ## 9.0.3 [elastic-security-9.0.3-release-notes]
 
 ### Features and enhancements [elastic-security-9.0.3-features-enhancements]

release-notes/elastic-security/known-issues.md

@@ -62,6 +62,9 @@ After enabling the Knowledge Base, you can manage entries using the AI Assistant
   }
   ```
 
+**Resolved**<br> 
+
+Resolved in {{stack}} 9.0.4
 :::
 
 :::{dropdown} The entity risk score feature may stop persisting risk score documents