diff --git a/phpBB/includes/session.php b/phpBB/includes/session.php
index 81fc33c924..80fd7e0687 100644
--- a/phpBB/includes/session.php
+++ b/phpBB/includes/session.php
@@ -138,7 +138,7 @@ class session
 		$this->time_now				= time();
 		$this->cookie_data			= array('u' => 0, 'k' => '');
 		$this->update_session_page	= $update_session_page;
-		$this->browser				= (!empty($_SERVER['HTTP_USER_AGENT'])) ? (string) $_SERVER['HTTP_USER_AGENT'] : '';
+		$this->browser				= (!empty($_SERVER['HTTP_USER_AGENT'])) ? htmlspecialchars((string) $_SERVER['HTTP_USER_AGENT']) : '';
 		$this->forwarded_for		= (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) ? (string) $_SERVER['HTTP_X_FORWARDED_FOR'] : '';
 		$this->host					= (!empty($_SERVER['HTTP_HOST'])) ? (string) $_SERVER['HTTP_HOST'] : 'localhost';
 		$this->page					= $this->extract_current_page($phpbb_root_path);