The extract function in PHP before 5.2.15 does not prevent use of the EXTR_OVERWRITE parameter to overwrite (1) the GLOBALS superglobal array and (2) the this variable, which allows context-dependent attackers to bypass intended access restrictions by modifying data structures that were not intended to depend on external input, a related issue to CVE-2005-2691 and CVE-2006-3758.