Mozilla developer Daniel Holbert reported that the fix to the plugin parameter array crash that was fixed in Firefox 3.6.7 caused a crash showing signs of memory corruption. In certain circumstances, properties in the plugin instance's parameter array could be freed prematurely leaving a dangling pointer that the plugin could execute, potentially calling into attacker-controlled memory.
Firefox 3.5.11 was also affected by the regression but the equivalent pointer was always initialized to NULL and not exploitable.