diff --git a/javascript-modules/engines/astro-engine/package.json b/javascript-modules/engines/astro-engine/package.json
index 93d0084e..ff9d202f 100644
--- a/javascript-modules/engines/astro-engine/package.json
+++ b/javascript-modules/engines/astro-engine/package.json
@@ -37,7 +37,7 @@
     "astro": "^2.0.0 || ^3.0.0",
     "esbuild": "^0.19.1",
     "esbuild-sass-plugin": "^2.13.0",
-    "postcss": "^8.4.29",
+    "postcss": "^8.4.31",
     "postcss-modules": "^6.0.0",
     "vite": "^4.2.1"
   },
diff --git a/javascript-modules/styles/package.json b/javascript-modules/styles/package.json
index ead791fd..86e684fc 100644
--- a/javascript-modules/styles/package.json
+++ b/javascript-modules/styles/package.json
@@ -28,7 +28,7 @@
     "@bookshop/helpers": "3.8.1",
     "fast-glob": "^3.2.7",
     "normalize-path": "^3.0.0",
-    "postcss": "^8.3.6",
+    "postcss": "^8.4.31",
     "postcss-load-config": "^3.1.0",
     "sass": "1.62.1"
   },
diff --git a/javascript-modules/yarn.lock b/javascript-modules/yarn.lock
index 1b10900f..d7ba6c46 100644
--- a/javascript-modules/yarn.lock
+++ b/javascript-modules/yarn.lock
@@ -583,7 +583,7 @@ __metadata:
     esbuild: ^0.19.1
     esbuild-sass-plugin: ^2.13.0
     nyc: ^15.1.0
-    postcss: ^8.4.29
+    postcss: ^8.4.31
     postcss-modules: ^6.0.0
     vite: ^4.2.1
   peerDependencies:
@@ -783,7 +783,7 @@ __metadata:
     fast-glob: ^3.2.7
     normalize-path: ^3.0.0
     nyc: ^15.1.0
-    postcss: ^8.3.6
+    postcss: ^8.4.31
     postcss-fluidvars: ^1.1.2
     postcss-load-config: ^3.1.0
     sass: 1.62.1
@@ -9952,7 +9952,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"postcss@npm:^8.3.6, postcss@npm:^8.4.27, postcss@npm:^8.4.29":
+"postcss@npm:^8.4.27":
   version: 8.4.30
   resolution: "postcss@npm:8.4.30"
   dependencies:
@@ -9963,6 +9963,17 @@ __metadata:
   languageName: node
   linkType: hard
 
+"postcss@npm:^8.4.31":
+  version: 8.4.31
+  resolution: "postcss@npm:8.4.31"
+  dependencies:
+    nanoid: ^3.3.6
+    picocolors: ^1.0.0
+    source-map-js: ^1.0.2
+  checksum: 1d8611341b073143ad90486fcdfeab49edd243377b1f51834dc4f6d028e82ce5190e4f11bb2633276864503654fb7cab28e67abdc0fbf9d1f88cad4a0ff0beea
+  languageName: node
+  linkType: hard
+
 "prebuild-install@npm:^7.1.1":
   version: 7.1.1
   resolution: "prebuild-install@npm:7.1.1"