Shiny app issue : 'filename.csv' is changing to '_filename.csv' when app is getting launched through web browser

Hello ! I have created one app which takes input url and generates CSV file to download. The app is working fine and i am able to download the file with a name 'filename.csv' when I am launching it through window pane but when I am using browser to launch the app , the filename that is getting downloaded is changing to '_filename.csv'.
Please help me on this.
Thanks !

This issue is resolved. I was doing one mistake while extracting the filename form the input url.