diff --git a/includes/Rest/Handler/MediaFileHandler.php b/includes/Rest/Handler/MediaFileHandler.php
index dfad7550e14..7e1df5f8150 100644
--- a/includes/Rest/Handler/MediaFileHandler.php
+++ b/includes/Rest/Handler/MediaFileHandler.php
@@ -10,7 +10,6 @@ use MediaWiki\Rest\LocalizedHttpException;
 use MediaWiki\Rest\Response;
 use MediaWiki\Rest\SimpleHandler;
 use RepoGroup;
-use User;
 use Wikimedia\Message\MessageValue;
 use Wikimedia\ParamValidator\ParamValidator;
 
@@ -66,10 +65,8 @@ class MediaFileHandler extends SimpleHandler {
 	private function getFile(): ?File {
 		if ( $this->file === false ) {
 			$page = $this->getPage();
-			// TODO: make RepoGroup::findFile take Authority
-			$user = User::newFromIdentity( $this->getAuthority()->getUser() );
 			$this->file =
-				$this->repoGroup->findFile( $page, [ 'private' => $user ] ) ?: null;
+				$this->repoGroup->findFile( $page, [ 'private' => $this->getAuthority() ] ) ?: null;
 		}
 		return $this->file;
 	}
diff --git a/includes/Rest/Handler/MediaLinksHandler.php b/includes/Rest/Handler/MediaLinksHandler.php
index 919140476ad..edd9227a7cc 100644
--- a/includes/Rest/Handler/MediaLinksHandler.php
+++ b/includes/Rest/Handler/MediaLinksHandler.php
@@ -9,7 +9,6 @@ use MediaWiki\Rest\LocalizedHttpException;
 use MediaWiki\Rest\Response;
 use MediaWiki\Rest\SimpleHandler;
 use RepoGroup;
-use User;
 use Wikimedia\Message\MessageValue;
 use Wikimedia\ParamValidator\ParamValidator;
 use Wikimedia\Rdbms\ILoadBalancer;
@@ -124,12 +123,11 @@ class MediaLinksHandler extends SimpleHandler {
 	private function processDbResults( $results ) {
 		// Using "private" here means an equivalent of the Action API's "anon-public-user-private"
 		// caching model would be necessary, if caching is ever added to this endpoint.
-		// TODO: make RepoGroup::findFiles take Authority
-		$user = User::newFromIdentity( $this->getAuthority()->getUser() );
-		$findTitles = array_map( static function ( $title ) use ( $user ) {
+		$performer = $this->getAuthority();
+		$findTitles = array_map( static function ( $title ) use ( $performer ) {
 			return [
 				'title' => $title,
-				'private' => $user,
+				'private' => $performer,
 			];
 		}, $results );
 
@@ -146,7 +144,7 @@ class MediaLinksHandler extends SimpleHandler {
 		];
 		$response = [];
 		foreach ( $files as $file ) {
-			$response[] = $this->getFileInfo( $file, $user, $transforms );
+			$response[] = $this->getFileInfo( $file, $performer, $transforms );
 		}
 
 		$response = [
diff --git a/includes/api/ApiQueryImageInfo.php b/includes/api/ApiQueryImageInfo.php
index 8468b3c93ca..7e7a0ea8684 100644
--- a/includes/api/ApiQueryImageInfo.php
+++ b/includes/api/ApiQueryImageInfo.php
@@ -87,11 +87,11 @@ class ApiQueryImageInfo extends ApiQueryBase {
 				}
 			}
 
-			$user = $this->getUser();
-			$findTitles = array_map( static function ( $title ) use ( $user ) {
+			$performer = $this->getAuthority();
+			$findTitles = array_map( static function ( $title ) use ( $performer ) {
 				return [
 					'title' => $title,
-					'private' => $user,
+					'private' => $performer,
 				];
 			}, $titles );
 
diff --git a/includes/filerepo/FileRepo.php b/includes/filerepo/FileRepo.php
index f0ce8e8e405..4889258da70 100644
--- a/includes/filerepo/FileRepo.php
+++ b/includes/filerepo/FileRepo.php
@@ -10,6 +10,7 @@
 use MediaWiki\Linker\LinkTarget;
 use MediaWiki\MediaWikiServices;
 use MediaWiki\Page\PageIdentity;
+use MediaWiki\Permissions\Authority;
 use MediaWiki\User\UserIdentity;
 
 /**
@@ -446,18 +447,19 @@ class FileRepo {
 	 *                   current version. An image object will be returned which was
 	 *                   created at the specified time (which may be archived or current).
 	 *   ignoreRedirect: If true, do not follow file redirects
-	 *   private:        If a User object, return restricted (deleted) files if the
-	 *                   user is allowed to view them. Otherwise, such files will not
-	 *                   be found. If set and not a User object, throws an exception
+	 *   private:        If an Authority object, return restricted (deleted) files if the
+	 *                   performer is allowed to view them. Otherwise, such files will not
+	 *                   be found. If set and not an Authority object, throws an exception.
+	 *                   Authority is only accepted since 1.37, User was required before.
 	 *   latest:         If true, load from the latest available data into File objects
 	 * @return File|bool False on failure
 	 * @throws InvalidArgumentException
 	 */
 	public function findFile( $title, $options = [] ) {
-		if ( !empty( $options['private'] ) && !( $options['private'] instanceof User ) ) {
+		if ( !empty( $options['private'] ) && !( $options['private'] instanceof Authority ) ) {
 			throw new InvalidArgumentException(
 				__METHOD__ . ' called with the `private` option set to something ' .
-				'other than a User object'
+				'other than an Authority object'
 			);
 		}
 
@@ -488,7 +490,7 @@ class FileRepo {
 					if ( !$img->isDeleted( File::DELETED_FILE ) ) {
 						return $img; // always OK
 					} elseif (
-						// If its not empty, its a User object
+						// If its not empty, its an Authority object
 						!empty( $options['private'] ) &&
 						$img->userCan( File::DELETED_FILE, $options['private'] )
 					) {
@@ -546,9 +548,9 @@ class FileRepo {
 
 				if (
 					!empty( $options['private'] ) &&
-					!( $options['private'] instanceof User )
+					!( $options['private'] instanceof Authority )
 				) {
-					$options['private'] = RequestContext::getMain()->getUser();
+					$options['private'] = RequestContext::getMain()->getAuthority();
 				}
 			} else {
 				$title = $item;
@@ -579,13 +581,13 @@ class FileRepo {
 	 * @param string $sha1 Base 36 SHA-1 hash
 	 * @param array $options Option array, same as findFile().
 	 * @return File|bool False on failure
-	 * @throws InvalidArgumentException if the `private` option is set and not a User object
+	 * @throws InvalidArgumentException if the `private` option is set and not an Authority object
 	 */
 	public function findFileFromKey( $sha1, $options = [] ) {
-		if ( !empty( $options['private'] ) && !( $options['private'] instanceof User ) ) {
+		if ( !empty( $options['private'] ) && !( $options['private'] instanceof Authority ) ) {
 			throw new InvalidArgumentException(
 				__METHOD__ . ' called with the `private` option set to something ' .
-				'other than a User object'
+				'other than an Authority object'
 			);
 		}
 
@@ -605,7 +607,7 @@ class FileRepo {
 				if ( !$img->isDeleted( File::DELETED_FILE ) ) {
 					return $img; // always OK
 				} elseif (
-					// If its not empty, its a User object
+					// If its not empty, its an Authority object
 					!empty( $options['private'] ) &&
 					$img->userCan( File::DELETED_FILE, $options['private'] )
 				) {
diff --git a/includes/filerepo/LocalRepo.php b/includes/filerepo/LocalRepo.php
index b5cd4a710e7..921c7da9b04 100644
--- a/includes/filerepo/LocalRepo.php
+++ b/includes/filerepo/LocalRepo.php
@@ -25,6 +25,7 @@
 use MediaWiki\Linker\LinkTarget;
 use MediaWiki\MediaWikiServices;
 use MediaWiki\Page\PageIdentity;
+use MediaWiki\Permissions\Authority;
 use Wikimedia\Rdbms\Database;
 use Wikimedia\Rdbms\IDatabase;
 use Wikimedia\Rdbms\IResultWrapper;
@@ -275,10 +276,10 @@ class LocalRepo extends FileRepo {
 			// Fallback to RequestContext::getMain should be replaced with a better
 			// way of setting the user that should be used; currently it needs to be
 			// set for each file individually. See T263033#6477586
-			$contextUser = RequestContext::getMain()->getUser();
-			$user = ( !empty( $search['private'] ) && $search['private'] instanceof User )
+			$contextPerformer = RequestContext::getMain()->getAuthority();
+			$performer = ( !empty( $search['private'] ) && $search['private'] instanceof Authority )
 				? $search['private']
-				: $contextUser;
+				: $contextPerformer;
 
 			return (
 				$file->exists() &&
@@ -287,7 +288,7 @@ class LocalRepo extends FileRepo {
 					( !empty( $search['time'] ) && $search['time'] === $file->getTimestamp() )
 				) &&
 				( !empty( $search['private'] ) || !$file->isDeleted( File::DELETED_FILE ) ) &&
-				$file->userCan( File::DELETED_FILE, $user )
+				$file->userCan( File::DELETED_FILE, $performer )
 			);
 		};
 
diff --git a/includes/filerepo/RepoGroup.php b/includes/filerepo/RepoGroup.php
index 8030c895956..694eb5ee312 100644
--- a/includes/filerepo/RepoGroup.php
+++ b/includes/filerepo/RepoGroup.php
@@ -113,11 +113,13 @@ class RepoGroup {
 	 *                   current version. An image object will be returned which was
 	 *                   created at the specified time.
 	 *   ignoreRedirect: If true, do not follow file redirects
-	 *   private:        If true, return restricted (deleted) files if the current
-	 *                   user is allowed to view them. Otherwise, such files will not
-	 *                   be found.
+	 *   private:        If Authority object, return restricted (deleted) files if the
+	 *                   performer is allowed to view them. Otherwise, such files will not
+	 *                   be found. Authority is only accepted since 1.37, User was required
+	 *                   before.
 	 *   latest:         If true, load from the latest available data into File objects
-	 * @phan-param array{time?:mixed,ignoreRedirect?:bool,private?:bool,latest?:bool} $options
+	 * @phpcs:ignore Generic.Files.LineLength
+	 * @phan-param array{time?:mixed,ignoreRedirect?:bool,private?:bool|MediaWiki\Permissions\Authority,latest?:bool} $options
 	 * @return File|bool False if title is not found
 	 */
 	public function findFile( $title, $options = [] ) {
diff --git a/includes/parser/Hook/BeforeParserFetchFileAndTitleHook.php b/includes/parser/Hook/BeforeParserFetchFileAndTitleHook.php
index 91deb73c947..6d36de5f812 100644
--- a/includes/parser/Hook/BeforeParserFetchFileAndTitleHook.php
+++ b/includes/parser/Hook/BeforeParserFetchFileAndTitleHook.php
@@ -22,7 +22,7 @@ interface BeforeParserFetchFileAndTitleHook {
 	 * @param Title $nt Image title
 	 * @param array &$options Array of options to RepoGroup::findFile. If it contains 'broken'
 	 *   as a key then the file will appear as a broken thumbnail.
-	 *   If it contains `private` as a key, the value must be a User object.
+	 *   If it contains `private` as a key, the value must be an Authority object.
 	 * @param string &$descQuery Query string to add to thumbnail URL
 	 * @return bool|void True or no return value to continue or false to abort
 	 */