diff --git a/mailmason/yarn.lock b/mailmason/yarn.lock
index 63569b750..ff60e9c33 100644
--- a/mailmason/yarn.lock
+++ b/mailmason/yarn.lock
@@ -2487,9 +2487,9 @@ ieee754@^1.1.4:
   integrity sha512-dcyqhDvX1C46lXZcVqCpK+FtMRQVdIMN6/Df5js2zouUsqG7I6sFxitIC+7KYK29KdXOLHdu9zL4sFnoVQnqaA==
 
 immutable@^4.0.0:
-  version "4.0.0"
-  resolved "https://registry.yarnpkg.com/immutable/-/immutable-4.0.0.tgz#b86f78de6adef3608395efb269a91462797e2c23"
-  integrity sha512-zIE9hX70qew5qTUjSS7wi1iwj/l7+m54KWU247nhM3v806UdGj1yDndXj+IOYxxtW9zyLI+xqFNZjTuDaLUqFw==
+  version "4.3.8"
+  resolved "https://registry.yarnpkg.com/immutable/-/immutable-4.3.8.tgz#02d183c7727fb2bb1d5d0380da0d779dce9296a7"
+  integrity sha512-d/Ld9aLbKpNwyl0KiM2CT1WYvkitQ1TSvmRtkcV8FKStiDoA7Slzgjmb/1G2yhKM1p0XeNOieaTbFZmU1d3Xuw==
 
 index-of@^0.2.0:
   version "0.2.0"