En este momento debería ser mas fácil la ubicación del plugin de adobe flash pero en este caso no se presento, así que esta es una solución mas fiable ....

Installing flash player for Chrome and Firefox

 Flash plugins are missing for Chrome and Firefox.

Workaround = Add the executable in the correct directories

 First download the kits at the following locations:

http://labs.adobe.com/technologies/flashplatformruntimes/flashplayer11/
http://get.adobe.com/flashplayer/?no_redirect

 Close both Chrome and Firefox and then do the following:

cd ~/Download
tar xvfz  flashplayer11_b2_install_lin_64_080811.tar.gz
chown root:root libflashplayer.so
 chmod 0644 libflashplayer.so
 cp -f libflashplayer.so /usr/lib/mozilla/plugins/
 rm -rf libflashplayer.so

tar xvfz install_flash_player_10_linux.tar.gz
 mkdir ~/.mozilla/plugins
 chown root:root libflashplayer.so
 chmod 0644 libflashplayer.so
 mv -f libflashplayer.so ~/.mozilla/plugins/

 Restart the browsers and this should fix it

FUENTE 

http://insidetrust.blogspot.com/2011/08/backtrack-5-r1-some-things-fixed-some.html