diff --git a/tests/functional/acp_attachments_test.php b/tests/functional/acp_attachments_test.php
new file mode 100644
index 0000000000..8b1fb2cc6d
--- /dev/null
+++ b/tests/functional/acp_attachments_test.php
@@ -0,0 +1,118 @@
+<?php
+/**
+*
+* This file is part of the phpBB Forum Software package.
+*
+* @copyright (c) phpBB Limited <https://www.phpbb.com>
+* @license GNU General Public License, version 2 (GPL-2.0)
+*
+* For full copyright and license information, please see
+* the docs/CREDITS.txt file.
+*
+*/
+
+/**
+ * @group functional
+ */
+class phpbb_functional_acp_attachments_test extends phpbb_functional_test_case
+{
+	private $path;
+
+	protected function setUp(): void
+	{
+		parent::setUp();
+		$this->path = __DIR__ . '/fixtures/files/';
+		$this->add_lang('posting');
+	}
+
+	protected function tearDown(): void
+	{
+		$iterator = new DirectoryIterator(__DIR__ . '/../../phpBB/files/');
+		foreach ($iterator as $fileinfo)
+		{
+			if (
+				$fileinfo->isDot()
+				|| $fileinfo->isDir()
+				|| $fileinfo->getFilename() === 'index.htm'
+				|| $fileinfo->getFilename() === '.htaccess'
+			)
+			{
+				continue;
+			}
+
+			unlink($fileinfo->getPathname());
+		}
+	}
+
+	private function upload_file($filename, $mimetype)
+	{
+		$crawler = self::$client->request(
+			'GET',
+			'posting.php?mode=reply&f=2&t=1&sid=' . $this->sid
+		);
+
+		$file_form_data = array_merge(['add_file' => $this->lang('ADD_FILE')], $this->get_hidden_fields($crawler, 'posting.php?mode=reply&f=2&t=1&sid=' . $this->sid));
+
+		$file = array(
+			'tmp_name' => $this->path . $filename,
+			'name' => $filename,
+			'type' => $mimetype,
+			'size' => filesize($this->path . $filename),
+			'error' => UPLOAD_ERR_OK,
+		);
+
+		$crawler = self::$client->request(
+			'POST',
+			'posting.php?mode=reply&t=1&sid=' . $this->sid,
+			$file_form_data,
+			array('fileupload' => $file)
+		);
+
+		return $crawler;
+	}
+
+	public function test_orphaned_attachments()
+	{
+		$this->login();
+		$this->add_lang(['common', 'acp/common', 'acp/attachments']);
+		$crawler = $this->upload_file('valid.jpg', 'image/jpeg');
+
+		// Ensure there was no error message rendered
+		$this->assertStringNotContainsString('<h2>' . $this->lang('INFORMATION') . '</h2>', $this->get_content());
+
+		// Also the file name should be in the first row of the files table
+		$this->assertEquals('valid.jpg', $crawler->filter('span.file-name > a')->text());
+		
+		$attach_link = $crawler->filter('span.file-name > a')->attr('href');
+		$attach_id = $this->get_parameter_from_link($attach_link, 'id');
+
+		// Set file time older than 3 hours to consider it orphan
+		$sql = 'UPDATE ' . ATTACHMENTS_TABLE . '
+			SET filetime = filetime - ' . 4*60*60 . '
+			WHERE attach_id = ' . (int) $attach_id;
+		$this->db->sql_query($sql);
+
+		$this->admin_login();
+		$crawler = self::request('GET', 'adm/index.php?sid=' . $this->sid . '&i=acp_attachments&mode=orphan');
+		$this->assertContainsLang('ACP_ORPHAN_ATTACHMENTS_EXPLAIN', $this->get_content());
+		$this->assertStringContainsString('valid.jpg', $crawler->filter('tbody a')->text());
+
+		$form = $crawler->selectButton($this->lang('SUBMIT'))->form([
+			"post_id[$attach_id]"	=> 99999, // Random
+		]);
+		$form["add[$attach_id]"]->tick();
+		$crawler = self::submit($form);
+
+		$this->assertContainsLang('UPLOADING_FILES', $this->get_content());
+		$this->assertStringContainsString($this->lang('UPLOADING_FILE_TO', 'valid.jpg', 99999), $this->get_content());
+		$this->assertStringContainsString($this->lang('UPLOAD_POST_NOT_EXIST', 'valid.jpg', 99999), $crawler->filter('span[class="error"]')->text());
+
+		// Delete the file
+		$form = $crawler->selectButton($this->lang('SUBMIT'))->form();
+		$form["delete[$attach_id]"]->tick();
+		$crawler = self::submit($form);
+
+		$this->assertContainsLang('NOTIFY', $crawler->filter('.successbox')->text());
+		$this->assertStringContainsString(strip_tags($this->lang('LOG_ATTACH_ORPHAN_DEL', 'valid.jpg')), $crawler->filter('.successbox > p')->text());
+	}
+}