diff --git a/src/security/external-content.ts b/src/security/external-content.ts
index b2022f6da82..ec2401ecebe 100644
--- a/src/security/external-content.ts
+++ b/src/security/external-content.ts
@@ -145,7 +145,7 @@ function foldMarkerChar(char: string): string {
 
 function foldMarkerText(input: string): string {
   return input.replace(
-    /[\uFF21-\uFF3A\uFF41-\uFF5A\uFF1C\uFF1E\u2329\u232A\u3008\u3009\u2039\u203A\u27E8\u27E9\uFE64\uFE65]/g,
+    /[\uFF21-\uFF3A\uFF41-\uFF5A\uFF1C\uFF1E\u2329\u232A\u3008\u3009\u2039\u203A\u27E8\u27E9\uFE64\uFE65\u00AB\u00BB\u300A\u300B\u27EA\u27EB\u276C\u276D\u276E\u276F]/g,
     (char) => foldMarkerChar(char),
   );
 }