diff --git a/eslint.config.mjs b/eslint.config.mjs
index fda42479f..1663523b5 100644
--- a/eslint.config.mjs
+++ b/eslint.config.mjs
@@ -118,6 +118,7 @@ export default [
             "web",
             "fluent-bundle",
             "fluent-dom",
+            "postcss-nesting",
             "postcss-values-parser",
             "stylelint",
             // See https://github.com/firebase/firebase-admin-node/discussions/1359.
diff --git a/package-lock.json b/package-lock.json
index f3ed4dda7..9760d795a 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -51,7 +51,7 @@
         "postcss": "^8.5.6",
         "postcss-dir-pseudo-class": "^9.0.1",
         "postcss-discard-comments": "^7.0.5",
-        "postcss-nesting": "^13.0.2",
+        "postcss-nesting": "^14.0.0",
         "postcss-values-parser": "^7.0.0",
         "prettier": "^3.8.1",
         "puppeteer": "^24.37.3",
@@ -1782,9 +1782,9 @@
       }
     },
     "node_modules/@csstools/selector-resolve-nested": {
-      "version": "3.1.0",
-      "resolved": "https://registry.npmjs.org/@csstools/selector-resolve-nested/-/selector-resolve-nested-3.1.0.tgz",
-      "integrity": "sha512-mf1LEW0tJLKfWyvn5KdDrhpxHyuxpbNwTIwOYLIvsTffeyOf85j5oIzfG0yosxDgx/sswlqBnESYUcQH0vgZ0g==",
+      "version": "4.0.0",
+      "resolved": "https://registry.npmjs.org/@csstools/selector-resolve-nested/-/selector-resolve-nested-4.0.0.tgz",
+      "integrity": "sha512-9vAPxmp+Dx3wQBIUwc1v7Mdisw1kbbaGqXUM8QLTgWg7SoPGYtXBsMXvsFs/0Bn5yoFhcktzxNZGNaUt0VjgjA==",
       "dev": true,
       "funding": [
         {
@@ -1798,16 +1798,16 @@
       ],
       "license": "MIT-0",
       "engines": {
-        "node": ">=18"
+        "node": ">=20.19.0"
       },
       "peerDependencies": {
-        "postcss-selector-parser": "^7.0.0"
+        "postcss-selector-parser": "^7.1.1"
       }
     },
     "node_modules/@csstools/selector-specificity": {
-      "version": "5.0.0",
-      "resolved": "https://registry.npmjs.org/@csstools/selector-specificity/-/selector-specificity-5.0.0.tgz",
-      "integrity": "sha512-PCqQV3c4CoVm3kdPhyeZ07VmBRdH2EpMFA/pd9OASpOEC3aXNGoqPDAZ80D0cLpMBxnmk0+yNhGsEx31hq7Gtw==",
+      "version": "6.0.0",
+      "resolved": "https://registry.npmjs.org/@csstools/selector-specificity/-/selector-specificity-6.0.0.tgz",
+      "integrity": "sha512-4sSgl78OtOXEX/2d++8A83zHNTgwCJMaR24FvsYL7Uf/VS8HZk9PTwR51elTbGqMuwH3szLvvOXEaVnqn0Z3zA==",
       "dev": true,
       "funding": [
         {
@@ -1821,10 +1821,10 @@
       ],
       "license": "MIT-0",
       "engines": {
-        "node": ">=18"
+        "node": ">=20.19.0"
       },
       "peerDependencies": {
-        "postcss-selector-parser": "^7.0.0"
+        "postcss-selector-parser": "^7.1.1"
       }
     },
     "node_modules/@csstools/utilities": {
@@ -10504,9 +10504,9 @@
       }
     },
     "node_modules/postcss-nesting": {
-      "version": "13.0.2",
-      "resolved": "https://registry.npmjs.org/postcss-nesting/-/postcss-nesting-13.0.2.tgz",
-      "integrity": "sha512-1YCI290TX+VP0U/K/aFxzHzQWHWURL+CtHMSbex1lCdpXD1SoR2sYuxDu5aNI9lPoXpKTCggFZiDJbwylU0LEQ==",
+      "version": "14.0.0",
+      "resolved": "https://registry.npmjs.org/postcss-nesting/-/postcss-nesting-14.0.0.tgz",
+      "integrity": "sha512-YGFOfVrjxYfeGTS5XctP1WCI5hu8Lr9SmntjfRC+iX5hCihEO+QZl9Ra+pkjqkgoVdDKvb2JccpElcowhZtzpw==",
       "dev": true,
       "funding": [
         {
@@ -10520,12 +10520,12 @@
       ],
       "license": "MIT-0",
       "dependencies": {
-        "@csstools/selector-resolve-nested": "^3.1.0",
-        "@csstools/selector-specificity": "^5.0.0",
-        "postcss-selector-parser": "^7.0.0"
+        "@csstools/selector-resolve-nested": "^4.0.0",
+        "@csstools/selector-specificity": "^6.0.0",
+        "postcss-selector-parser": "^7.1.1"
       },
       "engines": {
-        "node": ">=18"
+        "node": ">=20.19.0"
       },
       "peerDependencies": {
         "postcss": "^8.4"
@@ -12430,52 +12430,6 @@
         "@csstools/css-tokenizer": "^4.0.0"
       }
     },
-    "node_modules/stylelint/node_modules/@csstools/selector-resolve-nested": {
-      "version": "4.0.0",
-      "resolved": "https://registry.npmjs.org/@csstools/selector-resolve-nested/-/selector-resolve-nested-4.0.0.tgz",
-      "integrity": "sha512-9vAPxmp+Dx3wQBIUwc1v7Mdisw1kbbaGqXUM8QLTgWg7SoPGYtXBsMXvsFs/0Bn5yoFhcktzxNZGNaUt0VjgjA==",
-      "dev": true,
-      "funding": [
-        {
-          "type": "github",
-          "url": "https://github.com/sponsors/csstools"
-        },
-        {
-          "type": "opencollective",
-          "url": "https://opencollective.com/csstools"
-        }
-      ],
-      "license": "MIT-0",
-      "engines": {
-        "node": ">=20.19.0"
-      },
-      "peerDependencies": {
-        "postcss-selector-parser": "^7.1.1"
-      }
-    },
-    "node_modules/stylelint/node_modules/@csstools/selector-specificity": {
-      "version": "6.0.0",
-      "resolved": "https://registry.npmjs.org/@csstools/selector-specificity/-/selector-specificity-6.0.0.tgz",
-      "integrity": "sha512-4sSgl78OtOXEX/2d++8A83zHNTgwCJMaR24FvsYL7Uf/VS8HZk9PTwR51elTbGqMuwH3szLvvOXEaVnqn0Z3zA==",
-      "dev": true,
-      "funding": [
-        {
-          "type": "github",
-          "url": "https://github.com/sponsors/csstools"
-        },
-        {
-          "type": "opencollective",
-          "url": "https://opencollective.com/csstools"
-        }
-      ],
-      "license": "MIT-0",
-      "engines": {
-        "node": ">=20.19.0"
-      },
-      "peerDependencies": {
-        "postcss-selector-parser": "^7.1.1"
-      }
-    },
     "node_modules/stylelint/node_modules/balanced-match": {
       "version": "3.0.1",
       "resolved": "https://registry.npmjs.org/balanced-match/-/balanced-match-3.0.1.tgz",
diff --git a/package.json b/package.json
index 01a7ae9f4..c494a3b29 100644
--- a/package.json
+++ b/package.json
@@ -46,7 +46,7 @@
     "postcss": "^8.5.6",
     "postcss-dir-pseudo-class": "^9.0.1",
     "postcss-discard-comments": "^7.0.5",
-    "postcss-nesting": "^13.0.2",
+    "postcss-nesting": "^14.0.0",
     "postcss-values-parser": "^7.0.0",
     "prettier": "^3.8.1",
     "puppeteer": "^24.37.3",