diff --git a/.github/workflows/reusable-test-core-build-process.yml b/.github/workflows/reusable-test-core-build-process.yml
index 86f9e1ba1234a..e51646008ae9d 100644
--- a/.github/workflows/reusable-test-core-build-process.yml
+++ b/.github/workflows/reusable-test-core-build-process.yml
@@ -17,10 +17,15 @@ on:
         type: 'string'
         default: 'src'
       test-emoji:
-        description: 'Whether to run the grunt precommit:emoji script.'
+        description: 'Whether to run the precommit:emoji Grunt script.'
         required: false
         type: 'boolean'
         default: true
+      test-certificates:
+        description: 'Whether to run the certificate related Grunt scripts.'
+        required: false
+        type: 'boolean'
+        default: false
       save-build:
         description: 'Whether to save a ZIP of built WordPress as an artifact.'
         required: false
@@ -69,6 +74,21 @@ jobs:
           show-progress: ${{ runner.debug == '1' && 'true' || 'false' }}
           persist-credentials: false
 
+      # This date is used to ensure that the PHPCS cache is cleared at least once every week.
+      # http://man7.org/linux/man-pages/man1/date.1.html
+      - name: "Get last Monday's date"
+        id: get-date
+        if: ${{ inputs.test-certificates }}
+        run: echo "date=$(/bin/date -u --date='last Mon' "+%F")" >> "$GITHUB_OUTPUT"
+
+      # Since Composer dependencies are installed using `composer update` and no lock file is in version control,
+      # passing a custom cache suffix ensures that the cache is flushed at least once per week.
+      - name: Install Composer dependencies
+        if: ${{ inputs.test-certificates }}
+        uses: ramsey/composer-install@3cf229dc2919194e9e36783941438d17239e8520 # v3.1.1
+        with:
+          custom-cache-suffix: ${{ steps.get-date.outputs.date }}
+
       - name: Set up Node.js
         uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4.4.0
         with:
@@ -91,6 +111,10 @@ jobs:
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
+      - name: Ensure certificates files are updated
+        if: ${{ inputs.test-certificates }}
+        run: npm run grunt copy:certificates && npm run grunt build:certificates
+
       - name: Build WordPress to run from ${{ inputs.directory }}
         run: npm run ${{ inputs.directory == 'src' && 'build:dev' || 'build' }}
 
diff --git a/.github/workflows/test-build-processes.yml b/.github/workflows/test-build-processes.yml
index 587b6b02da290..9096d19838d84 100644
--- a/.github/workflows/test-build-processes.yml
+++ b/.github/workflows/test-build-processes.yml
@@ -59,6 +59,7 @@ jobs:
       matrix:
         os: [ 'ubuntu-24.04' ]
         directory: [ 'src', 'build' ]
+        test-certificates: [ true ]
         include:
           # Only prepare artifacts for Playground once.
           - os: 'ubuntu-24.04'
@@ -68,6 +69,7 @@ jobs:
     with:
       os: ${{ matrix.os }}
       directory: ${{ matrix.directory }}
+      test-certificates: ${{ matrix.test-certificates && true || false }}
       save-build: ${{ matrix.save-build && matrix.save-build || false }}
       prepare-playground: ${{ matrix.prepare-playground && matrix.prepare-playground || false }}
 
diff --git a/Gruntfile.js b/Gruntfile.js
index 56862d96b9b50..729f1117522e4 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -1584,10 +1584,69 @@ module.exports = function(grunt) {
 		'usebanner'
 	] );
 
-	grunt.registerTask( 'certificates:update', 'Updates the Composer package responsible for root certificate updates.', function() {
+	grunt.registerTask( 'certificates:upgrade-package', 'Upgrades the package responsible for supplying the certificate authority certificate store bundled with WordPress.', function() {
 		var done = this.async();
 		var flags = this.flags;
-		var args = [ 'update' ];
+		var spawn = require( 'child_process' ).spawnSync;
+		var fs = require( 'fs' );
+
+		// Ensure that `composer update` has been run and the dependency is installed.
+		if ( ! fs.existsSync( 'vendor' ) || ! fs.existsSync( 'vendor/composer' ) || ! fs.existsSync( 'vendor/composer/ca-bundle' ) ) {
+			grunt.log.error( 'composer/ca-bundle dependency is missing. Please run `composer update` before attempting to upgrade the certificate bundle.' );
+			done( false );
+			return;
+		}
+
+		/*
+		 * Because the `composer/ca-bundle` is pinned to an exact version to ensure upgrades are applied intentionally,
+		 * the `composer update` command will not upgrade the dependency. Instead, `composer require` must be called,
+		 * but the specific version being upgraded to must be known and passed to the command.
+		 */
+		var outdatedResult = spawn( 'composer', [ 'outdated', 'composer/ca-bundle', '--format=json' ] );
+
+		if ( outdatedResult.status !== 0 ) {
+			grunt.log.error( 'Failed to get the package information for composer/ca-bundle.' );
+			done( false );
+			return;
+		}
+
+		var packageInfo;
+		try {
+			var stdout = outdatedResult.stdout.toString().trim();
+			if ( ! stdout ) {
+				grunt.log.writeln( 'The latest version is already installed.' );
+				done( true );
+				return;
+			}
+			packageInfo = JSON.parse( stdout );
+		} catch ( e ) {
+			grunt.log.error( 'Failed to parse the package information for composer/ca-bundle.' );
+			done( false );
+			return;
+		}
+
+		// Check for the version information needed to perform the necessary comparisons.
+		if ( ! packageInfo.versions || ! packageInfo.versions[0] || ! packageInfo.latest ) {
+			grunt.log.error( 'Could not determine version information for composer/ca-bundle.' );
+			done( false );
+			return;
+		}
+
+		var currentVersion = packageInfo.versions[0];
+		var latestVersion = packageInfo.latest;
+
+		// Compare versions to ensure we actually need to update
+		if ( currentVersion === latestVersion ) {
+			grunt.log.writeln( 'The latest version is already installed: ' + latestVersion + '.' );
+			done( true );
+			return;
+		}
+
+		grunt.log.writeln( 'Installed version: ' + currentVersion );
+		grunt.log.writeln( 'New version found: ' + latestVersion );
+
+		// Upgrade to the latest version and change the pinned version in composer.json.
+		var args = [ 'require', 'composer/ca-bundle:' + latestVersion, '--dev' ];
 
 		grunt.util.spawn( {
 			cmd: 'composer',
@@ -1597,6 +1656,7 @@ module.exports = function(grunt) {
 			if ( flags.error && error ) {
 				done( false );
 			} else {
+				grunt.log.writeln( 'Successfully updated composer/ca-bundle to ' + latestVersion );
 				done( true );
 			}
 		} );
@@ -1607,7 +1667,7 @@ module.exports = function(grunt) {
 	] );
 
 	grunt.registerTask( 'certificates:upgrade', [
-		'certificates:update',
+		'certificates:upgrade-package',
 		'copy:certificates',
 		'build:certificates'
 	] );