classes/GoogleSpell.php in the PHP Spellchecker (aka Google Spellchecker) addon before 2.0.6.1 for TinyMCE, as used in Moodle 2.1.x before 2.1.10, 2.2.x before 2.2.7, 2.3.x before 2.3.4, and 2.4.x before 2.4.1 and other products, does not properly handle control characters, which allows remote attackers to trigger arbitrary outbound HTTP requests via a crafted string.