diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-revisions-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-revisions-controller.php
index 73a888d6eac48..f0f13b97f100f 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-revisions-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-revisions-controller.php
@@ -606,12 +606,23 @@ public function prepare_item_for_response( $item, $request ) {
 		// Restores the more descriptive, specific name for use within this method.
 		$post = $item;
 
+		/*
+		 * Save the previous global post so it can be restored before returning.
+		 * Preparing the revision sets up the global post and post data, which
+		 * must not leak into the rest of the request (e.g. the autosaves endpoint
+		 * is preloaded in the block editor, where a leaked global post can cause
+		 * the editor to be initialized with the wrong post).
+		 */
+		$previous_post = isset( $GLOBALS['post'] ) ? $GLOBALS['post'] : null;
+
 		$GLOBALS['post'] = $post;
 
 		setup_postdata( $post );
 
 		// Don't prepare the response body for HEAD requests.
 		if ( $request->is_method( 'HEAD' ) ) {
+			$this->reset_post_data( $previous_post );
+
 			/** This filter is documented in wp-includes/rest-api/endpoints/class-wp-rest-revisions-controller.php */
 			return apply_filters( 'rest_prepare_revision', new WP_REST_Response( array() ), $post, $request );
 		}
@@ -706,6 +717,8 @@ public function prepare_item_for_response( $item, $request ) {
 			$response->add_link( 'parent', rest_url( rest_get_route_for_post( $data['parent'] ) ) );
 		}
 
+		$this->reset_post_data( $previous_post );
+
 		/**
 		 * Filters a revision returned from the REST API.
 		 *
@@ -720,6 +733,27 @@ public function prepare_item_for_response( $item, $request ) {
 		return apply_filters( 'rest_prepare_revision', $response, $post, $request );
 	}
 
+	/**
+	 * Restores the global post to its previous value after preparing a revision.
+	 *
+	 * Preparing a revision overwrites the global post and post data via
+	 * setup_postdata(). This restores the global post that was in place
+	 * beforehand so the change does not leak into the rest of the request.
+	 *
+	 * @since 7.0.1
+	 *
+	 * @param WP_Post|null $previous_post The global post to restore, or null if there was none.
+	 */
+	private function reset_post_data( $previous_post ) {
+		if ( $previous_post instanceof WP_Post ) {
+			$GLOBALS['post'] = $previous_post;
+			setup_postdata( $previous_post );
+		} else {
+			unset( $GLOBALS['post'] );
+			wp_reset_postdata();
+		}
+	}
+
 	/**
 	 * Checks the post_date_gmt or modified_gmt and prepare any post or
 	 * modified date for single post output.
diff --git a/tests/phpunit/tests/rest-api/rest-autosaves-controller.php b/tests/phpunit/tests/rest-api/rest-autosaves-controller.php
index 7815f8ced23c9..11b294283c96d 100644
--- a/tests/phpunit/tests/rest-api/rest-autosaves-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-autosaves-controller.php
@@ -731,16 +731,34 @@ protected function check_get_autosave_response( $response, $autosave ) {
 		$this->assertSame( rest_url( '/wp/v2/' . $parent_base . '/' . $autosave->post_parent ), $links['parent'][0]['href'] );
 	}
 
-	public function test_get_item_sets_up_postdata() {
+	/**
+	 * The autosave's postdata should be set up while preparing the response,
+	 * so rendered fields reflect the autosave, without leaking into the global
+	 * post after the request completes.
+	 *
+	 * @ticket 65495
+	 */
+	public function test_get_item_sets_up_postdata_without_leaking_global_post() {
 		wp_set_current_user( self::$editor_id );
-		$request = new WP_REST_Request( 'GET', '/wp/v2/posts/' . self::$post_id . '/autosaves/' . self::$autosave_post_id );
-		rest_get_server()->dispatch( $request );
 
-		$post           = get_post();
-		$parent_post_id = wp_is_post_revision( $post->ID );
+		$GLOBALS['post'] = get_post( self::$post_id );
+		setup_postdata( $GLOBALS['post'] );
+
+		$request  = new WP_REST_Request( 'GET', '/wp/v2/posts/' . self::$post_id . '/autosaves/' . self::$autosave_post_id );
+		$response = rest_get_server()->dispatch( $request );
+		$data     = $response->get_data();
+
+		$autosave = get_post( self::$autosave_post_id );
 
-		$this->assertSame( $post->ID, self::$autosave_post_id );
-		$this->assertSame( $parent_post_id, self::$post_id );
+		// The rendered title reflects the autosave, proving postdata was set up during preparation.
+		$this->assertSame( get_the_title( $autosave->ID ), $data['title']['rendered'] );
+
+		// The global post is restored to the post that was set before the request.
+		$this->assertSame(
+			self::$post_id,
+			$GLOBALS['post']->ID,
+			'The global post should not leak the autosave after the request.'
+		);
 	}
 
 	public function test_update_item_draft_page_with_parent() {
diff --git a/tests/phpunit/tests/rest-api/rest-revisions-controller.php b/tests/phpunit/tests/rest-api/rest-revisions-controller.php
index 52011afcb9318..160617b0fbd24 100644
--- a/tests/phpunit/tests/rest-api/rest-revisions-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-revisions-controller.php
@@ -266,6 +266,78 @@ public function test_get_item() {
 		$this->assertSame( self::$editor_id, $data['author'] );
 	}
 
+	/**
+	 * Preparing a revision must not leak the revision into the global post.
+	 *
+	 * @ticket 65495
+	 *
+	 * @covers WP_REST_Revisions_Controller::prepare_item_for_response
+	 */
+	public function test_get_items_restores_global_post() {
+		wp_set_current_user( self::$editor_id );
+
+		$GLOBALS['post'] = get_post( self::$post_id );
+		setup_postdata( $GLOBALS['post'] );
+
+		$request = new WP_REST_Request( 'GET', '/wp/v2/posts/' . self::$post_id . '/revisions' );
+		$request->set_param( 'context', 'edit' );
+		$response = rest_get_server()->dispatch( $request );
+
+		$this->assertSame( 200, $response->get_status() );
+		$this->assertInstanceOf( 'WP_Post', $GLOBALS['post'], 'The global post should still be set after the request.' );
+		$this->assertSame(
+			self::$post_id,
+			$GLOBALS['post']->ID,
+			'The global post should be restored to the post that was set before the request.'
+		);
+	}
+
+	/**
+	 * Preparing a revision for a HEAD request must also restore the global post.
+	 *
+	 * @ticket 65495
+	 *
+	 * @covers WP_REST_Revisions_Controller::prepare_item_for_response
+	 */
+	public function test_get_items_head_request_restores_global_post() {
+		wp_set_current_user( self::$editor_id );
+
+		$GLOBALS['post'] = get_post( self::$post_id );
+		setup_postdata( $GLOBALS['post'] );
+
+		$request = new WP_REST_Request( 'HEAD', '/wp/v2/posts/' . self::$post_id . '/revisions' );
+		$request->set_param( 'context', 'edit' );
+		$response = rest_get_server()->dispatch( $request );
+
+		$this->assertSame( 200, $response->get_status() );
+		$this->assertInstanceOf( 'WP_Post', $GLOBALS['post'], 'The global post should still be set after a HEAD request.' );
+		$this->assertSame(
+			self::$post_id,
+			$GLOBALS['post']->ID,
+			'The global post should be restored after a HEAD request.'
+		);
+	}
+
+	/**
+	 * When there is no global post before the request, none should be set afterwards.
+	 *
+	 * @ticket 65495
+	 *
+	 * @covers WP_REST_Revisions_Controller::prepare_item_for_response
+	 */
+	public function test_get_items_without_global_post_leaves_it_unset() {
+		wp_set_current_user( self::$editor_id );
+
+		unset( $GLOBALS['post'] );
+
+		$request = new WP_REST_Request( 'GET', '/wp/v2/posts/' . self::$post_id . '/revisions' );
+		$request->set_param( 'context', 'edit' );
+		$response = rest_get_server()->dispatch( $request );
+
+		$this->assertSame( 200, $response->get_status() );
+		$this->assertArrayNotHasKey( 'post', $GLOBALS, 'The global post should not be set when there was none before the request.' );
+	}
+
 	/**
 	 * @dataProvider data_readable_http_methods
 	 * @ticket 56481
@@ -639,16 +711,32 @@ protected function check_get_revision_response( $response, $revision ) {
 		$this->assertSame( rest_url( '/wp/v2/' . $parent_base . '/' . $revision->post_parent ), $links['parent'][0]['href'] );
 	}
 
-	public function test_get_item_sets_up_postdata() {
+	/**
+	 * The revision's postdata should be set up while preparing the response,
+	 * so rendered fields reflect the revision, without leaking into the global
+	 * post after the request completes.
+	 *
+	 * @ticket 65495
+	 */
+	public function test_get_item_sets_up_postdata_without_leaking_global_post() {
 		wp_set_current_user( self::$editor_id );
-		$request = new WP_REST_Request( 'GET', '/wp/v2/posts/' . self::$post_id . '/revisions/' . $this->revision_id1 );
-		rest_get_server()->dispatch( $request );
 
-		$post           = get_post();
-		$parent_post_id = wp_is_post_revision( $post->ID );
+		$GLOBALS['post'] = get_post( self::$post_id );
+		setup_postdata( $GLOBALS['post'] );
 
-		$this->assertSame( $post->ID, $this->revision_id1 );
-		$this->assertSame( $parent_post_id, self::$post_id );
+		$request  = new WP_REST_Request( 'GET', '/wp/v2/posts/' . self::$post_id . '/revisions/' . $this->revision_id1 );
+		$response = rest_get_server()->dispatch( $request );
+		$data     = $response->get_data();
+
+		// The rendered title reflects the revision, proving postdata was set up during preparation.
+		$this->assertSame( get_the_title( $this->revision_id1 ), $data['title']['rendered'] );
+
+		// The global post is restored to the post that was set before the request.
+		$this->assertSame(
+			self::$post_id,
+			$GLOBALS['post']->ID,
+			'The global post should not leak the revision after the request.'
+		);
 	}
 
 	/**