diff --git a/yarn.lock b/yarn.lock
index bd23efe..9e6a8f4 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -998,7 +998,7 @@ circular-json@^0.3.1:
   version "0.3.3"
   resolved "https://registry.yarnpkg.com/circular-json/-/circular-json-0.3.3.tgz#815c99ea84f6809529d2f45791bdf82711352d66"
 
-clean-css@4.1.x, clean-css@^4.1.8:
+clean-css@4.1.x:
   version "4.1.9"
   resolved "https://registry.yarnpkg.com/clean-css/-/clean-css-4.1.9.tgz#35cee8ae7687a49b98034f70de00c4edd3826301"
   dependencies:
@@ -1011,6 +1011,12 @@ clean-css@^3.3.0:
     commander "2.8.x"
     source-map "0.4.x"
 
+clean-css@^4.1.8:
+  version "4.2.3"
+  resolved "https://registry.yarnpkg.com/clean-css/-/clean-css-4.2.3.tgz#507b5de7d97b48ee53d84adb0160ff6216380f78"
+  dependencies:
+    source-map "~0.6.0"
+
 cli-boxes@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/cli-boxes/-/cli-boxes-1.0.0.tgz#4fa917c3e59c94a004cd61f8ee509da651687143"
@@ -3669,6 +3675,10 @@ source-map@0.5.x, source-map@^0.5.3, source-map@^0.5.6, source-map@^0.5.7, sourc
   version "0.5.7"
   resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.5.7.tgz#8a039d2d1021d22d1ea14c80d8ea468ba2ef3fcc"
 
+source-map@~0.6.0:
+  version "0.6.1"
+  resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.6.1.tgz#74722af32e9614e9c287a8d0bbde48b5e2f1a263"
+
 spdx-correct@~1.0.0:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/spdx-correct/-/spdx-correct-1.0.2.tgz#4b3073d933ff51f3912f03ac5519498a4150db40"