diff --git a/src/sphinx_antsibull_ext/css/package-lock.json b/src/sphinx_antsibull_ext/css/package-lock.json
index 87540390..04324964 100644
--- a/src/sphinx_antsibull_ext/css/package-lock.json
+++ b/src/sphinx_antsibull_ext/css/package-lock.json
@@ -9,7 +9,7 @@
         "cssnano": "^7.0.6",
         "postcss": "^8.4.48",
         "postcss-cli": "^11.0.0",
-        "sass": "^1.80.6"
+        "sass": "^1.81.0"
       }
     },
     "node_modules/@nodelib/fs.scandir": {
@@ -942,9 +942,9 @@
       }
     },
     "node_modules/immutable": {
-      "version": "4.3.5",
-      "resolved": "https://registry.npmjs.org/immutable/-/immutable-4.3.5.tgz",
-      "integrity": "sha512-8eabxkth9gZatlwl5TBuJnCsoTADlL6ftEr7A4qgdaTsPyreilDSnUk57SO+jfKcNtxPa22U5KK6DSeAYhpBJw=="
+      "version": "5.0.2",
+      "resolved": "https://registry.npmjs.org/immutable/-/immutable-5.0.2.tgz",
+      "integrity": "sha512-1NU7hWZDkV7hJ4PJ9dur9gTNQ4ePNPN4k9/0YhwjzykTi/+3Q5pF93YU5QoVj8BuOnhLgaY8gs0U2pj4kSYVcw=="
     },
     "node_modules/is-binary-path": {
       "version": "2.1.0",
@@ -1740,12 +1740,12 @@
       }
     },
     "node_modules/sass": {
-      "version": "1.80.6",
-      "resolved": "https://registry.npmjs.org/sass/-/sass-1.80.6.tgz",
-      "integrity": "sha512-ccZgdHNiBF1NHBsWvacvT5rju3y1d/Eu+8Ex6c21nHp2lZGLBEtuwc415QfiI1PJa1TpCo3iXwwSRjRpn2Ckjg==",
+      "version": "1.81.0",
+      "resolved": "https://registry.npmjs.org/sass/-/sass-1.81.0.tgz",
+      "integrity": "sha512-Q4fOxRfhmv3sqCLoGfvrC9pRV8btc0UtqL9mN6Yrv6Qi9ScL55CVH1vlPP863ISLEEMNLLuu9P+enCeGHlnzhA==",
       "dependencies": {
         "chokidar": "^4.0.0",
-        "immutable": "^4.0.0",
+        "immutable": "^5.0.2",
         "source-map-js": ">=0.6.2 <2.0.0"
       },
       "bin": {
diff --git a/src/sphinx_antsibull_ext/css/package.json b/src/sphinx_antsibull_ext/css/package.json
index 8797bd36..15a19962 100644
--- a/src/sphinx_antsibull_ext/css/package.json
+++ b/src/sphinx_antsibull_ext/css/package.json
@@ -4,6 +4,6 @@
     "cssnano": "^7.0.6",
     "postcss": "^8.4.48",
     "postcss-cli": "^11.0.0",
-    "sass": "^1.80.6"
+    "sass": "^1.81.0"
   }
 }