An adware purveyor has apparently used two previously unknown <A HREF="http://zdnet.com.com/2100-1105_2-5229707.html?tag=zdnn.alert">security flaws in Microsoft's Internet Explorer</A> browser to install a toolbar on victims' computers that triggers pop-up ads. One flaw lets an attacker run a program on a victim's machine, while the other enables malicious code to "cross zones," or run with privileges higher than normal.