diff --git a/modules/ROOT/pages/8.4.0-release-notes.adoc b/modules/ROOT/pages/8.4.0-release-notes.adoc
index 43cf05feb9..b526ed4ccd 100644
--- a/modules/ROOT/pages/8.4.0-release-notes.adoc
+++ b/modules/ROOT/pages/8.4.0-release-notes.adoc
@@ -96,7 +96,14 @@ For information on the **Export to PDF** plugin, see xref:exportpdf.adoc[Export
 
 The {productname} {release-version} release includes an accompanying release of the **Media Optimizer** premium plugin.
 
-**Media Optimizer** includes the following addition.
+**Media Optimizer** includes the following addition and fix.
+
+==== Third-party library icons appear in formats when using Media Optimiser plugin together with CSS plugin
+// #TINY-13515
+
+Previously, when the Media Optimiser plugin was used together with the importcss plugin, the previous version of `uc-video` required importing external styles. The importcss plugin detected these imports and added them to the format menu, causing third-party library icons to appear in the formats UI. These icons were not part of the official TinyMCE icon pack and created a confusing and inconsistent UI experience.
+
+In {productname} {release-version}, the `uc-video` package was upgraded to a version that has styles self-contained in the web component. The importcss plugin no longer detects `uc-video` styles, so third-party icons no longer appear in the formats UI.
 
 ==== SVG images can now be uploaded.
 // #TINY-13708