Document 8.15 memory usage regression as a known issue.

CHANGELOG.asciidoc

@@ -7,6 +7,12 @@
 === Beats version 8.15.3
 https://github.com/elastic/beats/compare/v8.15.2\...v8.15.3[View commits]
 
+==== Known issues
+
+*Affecting all Beats*
+
+- Memory usage is not correctly limited by the number of events actively in the memory queue, but rather the maximum size of the memory queue regardless of usage. {issue}41355[41355]
+
 ==== Breaking changes
 
 *Filebeat*
@@ -48,6 +54,12 @@ https://github.com/elastic/beats/compare/v8.15.2\...v8.15.3[View commits]
 === Beats version 8.15.2
 https://github.com/elastic/beats/compare/v8.15.1\...v8.15.2[View commits]
 
+==== Known issues
+
+*Affecting all Beats*
+
+- Memory usage is not correctly limited by the number of events actively in the memory queue, but rather the maximum size of the memory queue regardless of usage. {issue}41355[41355]
+
 ==== Bugfixes
 
 *Affecting all Beats*
@@ -100,6 +112,7 @@ https://github.com/elastic/beats/compare/v8.15.0\...v8.15.1[View commits]
 *Affecting all Beats*
 
 - Beats stop publishing data after a network error unless restarted. Avoid upgrading to 8.15.1. Affected Beats log `Get \"https://${ELASTICSEARCH_HOST}:443\": context canceled` repeatedly. {issue}40705{40705}
+- Memory usage is not correctly limited by the number of events actively in the memory queue, but rather the maximum size of the memory queue regardless of usage. {issue}41355[41355]
 
 ==== Bugfixes
 
@@ -152,6 +165,7 @@ https://github.com/elastic/beats/compare/v8.14.3\...v8.15.0[View commits]
 *Filebeat*
 
 - The Azure EventHub input in Filebeat is not found when running on Windows. Please refrain from upgrading to 8.15. See {issue}40608[40608] for details.
+- Memory usage is not correctly limited by the number of events actively in the memory queue, but rather the maximum size of the memory queue regardless of usage. {issue}41355[41355]
 
 ==== Breaking changes