How Firefox finds out download file name on cnet.com?

Using Fiddler and also Live HTTP Headers I tried to find out how Firefox knows what's the name of file and shows it at Save As dialog.There's a Content-Disposition in headers which has no file name: Content-Disposition: attachment which should be Content-Disposition: attachment; filename=.... 开发者_如何学运维Then how Firefox knows the file name ?

sample URL:

http://download.cnet.com/Flock/3000-2356_4-75210908.html?tag=contentMain;contentBody

The site redirects to

http://software-files-l.cnet.com/s/software/11/57/77/21/FlockSetup_1_2_213_0_3PD.exe?e=1289760172&h=6a553713be5eede3474e961542ad7db8&lop=link&ptype=1901&ontid=2356&siteId=4&edId=3&spi=27176364f3c3621b51584f0aa2c67dc6&pid=11577721&psid=75210908&fileName=FlockSetup_1_2_213_0_3PD.exe

BThe filename portion of the URL (between the last / and the querystring) is FlockSetup_1_2_213_0_3PD.exe.

My immediate guess would be from the filename part of the URL of the file you're downloading.

For example: http://example.com/dir/file.ext has file.ext as filename part.