trojan help kinda

so i was searching adobes site and downloaded something from

 

adobe.com/cfusion/tdrc/index.cm?product=photoshop

 

 

then norton scaned it found threat deleted it and i didnt care if it was removed i deleted the installer. anyway the threat was

 

http://www.symantec.com/security_response/writeup.jsp?docid=2011-102713-4647-99&vid=42297&product=Norton%20Internet%20Security&version=20.2.1.22&plang=sym:EN&layouttype=TrialWare&buildname=Retail&heartbeatID=39349466-7C0A-4759-A6DA-1B381403A336&env=prod&vendorid=&plid=2&plgid=2&skup=21171960&skum=21234697&skuf=21171505&endpointid=%7B39349466-7C0A-4759-A6DA-1B381403A336%7D&partnerid=&lic_type=512&lic_attr=21124114&psn=G3QG89JY63DQ&osvers=6.1&oslocale=iso:CAN&oslang=iso:ENG&os=windows

 

what is it exactly and what does it do why would adobe have a trojan in its stuff . never know who you ca trust huh and i thought all trojans where high risk this says low risk info would be very appreciated

 

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