diff --git a/lib/compat/wordpress-6.5/fonts/class-wp-font-collection.php b/lib/compat/wordpress-6.5/fonts/class-wp-font-collection.php
index f628b90d31b00..9f5946fbe5dcc 100644
--- a/lib/compat/wordpress-6.5/fonts/class-wp-font-collection.php
+++ b/lib/compat/wordpress-6.5/fonts/class-wp-font-collection.php
@@ -31,7 +31,7 @@ final class WP_Font_Collection {
 		 *
 		 * @since 6.5.0
 		 *
-		 * @var array
+		 * @var array|WP_Error|null
 		 */
 		private $data;
 
@@ -40,58 +40,10 @@ final class WP_Font_Collection {
 		 *
 		 * @since 6.5.0
 		 *
-		 * @var string
+		 * @var string|null
 		 */
 		private $src;
 
-		/**
-		 * Font collection sanitization schema.
-		 *
-		 * @since 6.5.0
-		 *
-		 * @var array
-		 */
-		const COLLECTION_SANITIZATION_SCHEMA = array(
-			'name'          => 'sanitize_text_field',
-			'description'   => 'sanitize_text_field',
-			'font_families' => array(
-				array(
-					'font_family_settings' => array(
-						'name'       => 'sanitize_text_field',
-						'slug'       => 'sanitize_title',
-						'fontFamily' => 'sanitize_text_field',
-						'preview'    => 'sanitize_url',
-						'fontFace'   => array(
-							array(
-								'fontFamily'            => 'sanitize_text_field',
-								'fontStyle'             => 'sanitize_text_field',
-								'fontWeight'            => 'sanitize_text_field',
-								'src'                   => 'WP_Font_Collection::sanitize_src_property',
-								'preview'               => 'sanitize_url',
-								'fontDisplay'           => 'sanitize_text_field',
-								'fontStretch'           => 'sanitize_text_field',
-								'ascentOverride'        => 'sanitize_text_field',
-								'descentOverride'       => 'sanitize_text_field',
-								'fontVariant'           => 'sanitize_text_field',
-								'fontFeatureSettings'   => 'sanitize_text_field',
-								'fontVariationSettings' => 'sanitize_text_field',
-								'lineGapOverride'       => 'sanitize_text_field',
-								'sizeAdjust'            => 'sanitize_text_field',
-								'unicodeRange'          => 'sanitize_text_field',
-							),
-						),
-					),
-					'categories'           => array( 'sanitize_title' ),
-				),
-			),
-			'categories'    => array(
-				array(
-					'name' => 'sanitize_text_field',
-					'slug' => 'sanitize_title',
-				),
-			),
-		);
-
 		/**
 		 * WP_Font_Collection constructor.
 		 *
@@ -110,10 +62,10 @@ final class WP_Font_Collection {
 		public function __construct( $slug, $data_or_file ) {
 			$this->slug = sanitize_title( $slug );
 
-			// Data or json are lazy loaded and validated in get_data().
 			if ( is_array( $data_or_file ) ) {
-				$this->data = $data_or_file;
+				$this->data = $this->sanitize_and_validate_data( $data_or_file );
 			} else {
+				// JSON data is lazy loaded by ::get_data().
 				$this->src = $data_or_file;
 			}
 
@@ -135,30 +87,25 @@ public function __construct( $slug, $data_or_file ) {
 		 * @return array|WP_Error An array containing the font collection data, or a WP_Error on failure.
 		 */
 		public function get_data() {
-			// If we have a JSON config, load it and cache the data if it's valid.
+			// If the collection uses JSON data, load it and cache the data/error.
 			if ( $this->src && empty( $this->data ) ) {
-				$data = $this->load_from_json( $this->src );
-				if ( is_wp_error( $data ) ) {
-					return $data;
-				}
-
-				$this->data = $data;
+				$this->data = $this->load_from_json( $this->src );
 			}
 
-			// Validate required properties are not empty.
-			$data = $this->validate_andd_sanitize( $this->data );
-			if ( is_wp_error( $data ) ) {
-				return $data;
+			$data_or_error = $this->data;
+
+			if ( ! is_wp_error( $data_or_error ) ) {
+				// Set defaults for optional properties.
+				$data_or_error = wp_parse_args(
+					$this->data,
+					array(
+						'description' => '',
+						'categories'  => array(),
+					)
+				);
 			}
 
-			// Set defaults for optional properties.
-			return wp_parse_args(
-				$data,
-				array(
-					'description' => '',
-					'categories'  => array(),
-				)
-			);
+			return $data_or_error;
 		}
 
 		/**
@@ -199,7 +146,7 @@ private function load_from_file( $file ) {
 				return new WP_Error( 'font_collection_decode_error', __( 'Error decoding the font collection JSON file contents.', 'gutenberg' ) );
 			}
 
-			return $data;
+			return $this->sanitize_and_validate_data( $data );
 		}
 
 		/**
@@ -228,8 +175,8 @@ private function load_from_url( $url ) {
 					return new WP_Error( 'font_collection_decode_error', __( 'Error decoding the font collection data from the REST response JSON.', 'gutenberg' ) );
 				}
 
-				// Make sure the data is valid before caching it.
-				$data = $this->validate_andd_sanitize( $data );
+				// Make sure the data is valid before storing it in a transient.
+				$data = $this->sanitize_and_validate_data( $data );
 				if ( is_wp_error( $data ) ) {
 					return $data;
 				}
@@ -241,15 +188,18 @@ private function load_from_url( $url ) {
 		}
 
 		/**
-		 * Validates the font collection configuration.
+		 * Sanitizes and validates the font collection data.
 		 *
 		 * @since 6.5.0
 		 *
-		 * @param array $data Font collection configuration to validate.
-		 * @return array|WP_Error Array of data if valid, otherwise a WP_Error instance.
+		 * @param array $data Font collection data.
+		 *
+		 * @return array|WP_Error Sanitized data if valid, otherwise a WP_Error instance.
 		 */
-		private function validate_andd_sanitize( $data ) {
-			$data                = WP_Font_Utils::sanitize_from_schema( $data, self::COLLECTION_SANITIZATION_SCHEMA );
+		private function sanitize_and_validate_data( $data ) {
+			$schema = self::get_sanitization_schema();
+			$data   = WP_Font_Utils::sanitize_from_schema( $data, $schema );
+
 			$required_properties = array( 'name', 'font_families' );
 			foreach ( $required_properties as $property ) {
 				if ( empty( $data[ $property ] ) ) {
@@ -268,26 +218,57 @@ private function validate_andd_sanitize( $data ) {
 		}
 
 		/**
-		 * Sanitizes a src property.
-		 *
-		 * Font faces can have a src property consisting on a string or an array of strings.
-		 * This method sanitizes the src property value.
+		 * Retrieves the font collection sanitization schema.
 		 *
 		 * @since 6.5.0
 		 *
-		 * @param string|array $value src property value to sanitize.
-		 *
-		 * @return string|array Sanitized URL value.
+		 * @return array Font collection sanitization schema.
 		 */
-		public static function sanitize_src_property( $value ) {
-			if ( is_array( $value ) ) {
-				foreach ( $value as $key => $val ) {
-					$value[ $key ] = sanitize_url( $val );
-				}
-				return $value;
-			}
-
-			return sanitize_url( $value );
+		private static function get_sanitization_schema() {
+			return array(
+				'name'          => 'sanitize_text_field',
+				'description'   => 'sanitize_text_field',
+				'font_families' => array(
+					array(
+						'font_family_settings' => array(
+							'name'       => 'sanitize_text_field',
+							'slug'       => 'sanitize_title',
+							'fontFamily' => 'sanitize_text_field',
+							'preview'    => 'sanitize_url',
+							'fontFace'   => array(
+								array(
+									'fontFamily'          => 'sanitize_text_field',
+									'fontStyle'           => 'sanitize_text_field',
+									'fontWeight'          => 'sanitize_text_field',
+									'src'                 => function ( $value ) {
+										return is_array( $value )
+											? array_map( 'sanitize_text_field', $value )
+											: sanitize_text_field( $value );
+									},
+									'preview'             => 'sanitize_url',
+									'fontDisplay'         => 'sanitize_text_field',
+									'fontStretch'         => 'sanitize_text_field',
+									'ascentOverride'      => 'sanitize_text_field',
+									'descentOverride'     => 'sanitize_text_field',
+									'fontVariant'         => 'sanitize_text_field',
+									'fontFeatureSettings' => 'sanitize_text_field',
+									'fontVariationSettings' => 'sanitize_text_field',
+									'lineGapOverride'     => 'sanitize_text_field',
+									'sizeAdjust'          => 'sanitize_text_field',
+									'unicodeRange'        => 'sanitize_text_field',
+								),
+							),
+						),
+						'categories'           => array( 'sanitize_title' ),
+					),
+				),
+				'categories'    => array(
+					array(
+						'name' => 'sanitize_text_field',
+						'slug' => 'sanitize_title',
+					),
+				),
+			);
 		}
 	}
 }
diff --git a/lib/compat/wordpress-6.5/fonts/class-wp-font-utils.php b/lib/compat/wordpress-6.5/fonts/class-wp-font-utils.php
index 792a5aaa80eef..415e9e7f1f350 100644
--- a/lib/compat/wordpress-6.5/fonts/class-wp-font-utils.php
+++ b/lib/compat/wordpress-6.5/fonts/class-wp-font-utils.php
@@ -158,7 +158,7 @@ public static function sanitize_from_schema( $tree, $schema ) {
 				}
 
 				$is_value_array  = is_array( $value );
-				$is_schema_array = is_array( $schema[ $key ] );
+				$is_schema_array = is_array( $schema[ $key ] ) && ! is_callable( $schema[ $key ] );
 
 				if ( $is_value_array && $is_schema_array ) {
 					if ( wp_is_numeric_array( $value ) ) {
@@ -193,6 +193,7 @@ public static function sanitize_from_schema( $tree, $schema ) {
 		 * Apply the sanitizer to the value.
 		 *
 		 * @since 6.5.0
+		 *
 		 * @param mixed $value The value to sanitize.
 		 * @param mixed $sanitizer The sanitizer to apply.
 		 *
diff --git a/phpunit/tests/fonts/font-library/wpFontCollection/__construct.php b/phpunit/tests/fonts/font-library/wpFontCollection/__construct.php
index 53a1ce0a5482b..a0693ce341456 100644
--- a/phpunit/tests/fonts/font-library/wpFontCollection/__construct.php
+++ b/phpunit/tests/fonts/font-library/wpFontCollection/__construct.php
@@ -14,8 +14,12 @@ class Tests_Fonts_WpFontCollection_Construct extends WP_UnitTestCase {
 
 	public function test_should_do_it_wrong_with_invalid_slug() {
 		$this->setExpectedIncorrectUsage( 'WP_Font_Collection::__construct' );
+		$mock_collection_data = array(
+			'name'          => 'Test Collection',
+			'font_families' => array( 'mock ' ),
+		);
 
-		$collection = new WP_Font_Collection( 'slug with spaces', array() );
+		$collection = new WP_Font_Collection( 'slug with spaces', $mock_collection_data );
 
 		$this->assertSame( 'slug-with-spaces', $collection->slug, 'Slug is not sanitized.' );
 	}
diff --git a/phpunit/tests/fonts/font-library/wpFontCollection/getData.php b/phpunit/tests/fonts/font-library/wpFontCollection/getData.php
index c77456dde1405..1cb16e271db61 100644
--- a/phpunit/tests/fonts/font-library/wpFontCollection/getData.php
+++ b/phpunit/tests/fonts/font-library/wpFontCollection/getData.php
@@ -167,14 +167,14 @@ public function data_create_font_collection() {
 										'fontFamily' => 'Open Sans',
 										'fontStyle'  => 'normal',
 										'fontWeight' => '400',
-										'src'        => 'https://example.com/src-as-string.ttf?a=scriptalert(xss)/script',
+										'src'        => 'https://example.com/src-as-string.ttf?a=',
 									),
 									array(
 										'fontFamily' => 'Open Sans',
 										'fontStyle'  => 'normal',
 										'fontWeight' => '400',
 										'src'        => array(
-											'https://example.com/src-as-array.woff2?a=scriptalert(xss)/script',
+											'https://example.com/src-as-array.woff2?a=',
 											'https://example.com/src-as-array.ttf',
 										),
 									),
@@ -195,7 +195,7 @@ public function data_create_font_collection() {
 	 * @param array $config Font collection config.
 	 */
 	public function test_should_error_when_missing_properties( $config ) {
-		$this->setExpectedIncorrectUsage( 'WP_Font_Collection::validate_andd_sanitize' );
+		$this->setExpectedIncorrectUsage( 'WP_Font_Collection::sanitize_and_validate_data' );
 
 		$collection = new WP_Font_Collection( 'my-collection', $config );
 		$data       = $collection->get_data();
diff --git a/phpunit/tests/fonts/font-library/wpFontLibrary/getFontCollection.php b/phpunit/tests/fonts/font-library/wpFontLibrary/getFontCollection.php
index bc6b6d6005d1c..2c246de80b8b9 100644
--- a/phpunit/tests/fonts/font-library/wpFontLibrary/getFontCollection.php
+++ b/phpunit/tests/fonts/font-library/wpFontLibrary/getFontCollection.php
@@ -13,7 +13,12 @@
 class Tests_Fonts_WpFontLibrary_GetFontCollection extends WP_Font_Library_UnitTestCase {
 
 	public function test_should_get_font_collection() {
-		wp_register_font_collection( 'my-font-collection', array( 'font_families' => array( 'mock' ) ) );
+		$mock_collection_data = array(
+			'name'          => 'Test Collection',
+			'font_families' => array( 'mock' ),
+		);
+
+		wp_register_font_collection( 'my-font-collection', $mock_collection_data );
 		$font_collection = WP_Font_Library::get_font_collection( 'my-font-collection' );
 		$this->assertInstanceOf( 'WP_Font_Collection', $font_collection );
 	}
diff --git a/phpunit/tests/fonts/font-library/wpFontLibrary/registerFontCollection.php b/phpunit/tests/fonts/font-library/wpFontLibrary/registerFontCollection.php
index 1ba9ab1d32fb4..24529d0dd090b 100644
--- a/phpunit/tests/fonts/font-library/wpFontLibrary/registerFontCollection.php
+++ b/phpunit/tests/fonts/font-library/wpFontLibrary/registerFontCollection.php
@@ -13,6 +13,7 @@
 class Tests_Fonts_WpFontLibrary_RegisterFontCollection extends WP_Font_Library_UnitTestCase {
 	public function test_should_register_font_collection() {
 		$config = array(
+			'name'          => 'My Collection',
 			'font_families' => array( 'mock' ),
 		);
 
@@ -21,14 +22,19 @@ public function test_should_register_font_collection() {
 	}
 
 	public function test_should_return_error_if_slug_is_repeated() {
+		$mock_collection_data = array(
+			'name'          => 'Test Collection',
+			'font_families' => array( 'mock' ),
+		);
+
 		// Register first collection.
-		$collection1 = WP_Font_Library::register_font_collection( 'my-collection-1', array( 'font_families' => array( 'mock' ) ) );
+		$collection1 = WP_Font_Library::register_font_collection( 'my-collection-1', $mock_collection_data );
 		$this->assertInstanceOf( 'WP_Font_Collection', $collection1, 'A collection should be registered.' );
 
 		// Expects a _doing_it_wrong notice.
 		$this->setExpectedIncorrectUsage( 'WP_Font_Library::register_font_collection' );
 
 		// Try to register a second collection with same slug.
-		WP_Font_Library::register_font_collection( 'my-collection-1', array( 'font_families' => array( 'mock' ) ) );
+		WP_Font_Library::register_font_collection( 'my-collection-1', $mock_collection_data );
 	}
 }
diff --git a/phpunit/tests/fonts/font-library/wpFontLibrary/unregisterFontCollection.php b/phpunit/tests/fonts/font-library/wpFontLibrary/unregisterFontCollection.php
index 9546d0082eff9..657d3bb07aaaf 100644
--- a/phpunit/tests/fonts/font-library/wpFontLibrary/unregisterFontCollection.php
+++ b/phpunit/tests/fonts/font-library/wpFontLibrary/unregisterFontCollection.php
@@ -13,9 +13,14 @@
 class Tests_Fonts_WpFontLibrary_UnregisterFontCollection extends WP_Font_Library_UnitTestCase {
 
 	public function test_should_unregister_font_collection() {
+		$mock_collection_data = array(
+			'name'          => 'Test Collection',
+			'font_families' => array( 'mock' ),
+		);
+
 		// Registers two mock font collections.
-		WP_Font_Library::register_font_collection( 'mock-font-collection-1', array( 'font_families' => array( 'mock' ) ) );
-		WP_Font_Library::register_font_collection( 'mock-font-collection-2', array( 'font_families' => array( 'mock' ) ) );
+		WP_Font_Library::register_font_collection( 'mock-font-collection-1', $mock_collection_data );
+		WP_Font_Library::register_font_collection( 'mock-font-collection-2', $mock_collection_data );
 
 		// Unregister mock font collection.
 		WP_Font_Library::unregister_font_collection( 'mock-font-collection-1' );
@@ -36,6 +41,6 @@ public function unregister_non_existing_collection() {
 		// Unregisters non-existing font collection.
 		WP_Font_Library::unregister_font_collection( 'non-existing-collection' );
 		$collections = WP_Font_Library::get_font_collections();
-		$this->assertEmpty( $collections, 'Should not be registered collections.' );
+		$this->assertEmpty( $collections, 'No collections should be registered.' );
 	}
 }