Add extension

[AadMetz]

When I export a file with the Save for web option, Photoshop selects the whole name of the file (File name and extension). When you change the name, you have to add the extension by hand.

It would be nice when Photoshop only selected the name of the file and remains the extension (see attached files)

Photoshop selected the whole name.

This would be better....

[c.pfaffenbichler]

The issue sounds somewhat like an existing Bug Report 

https://feedback.photoshop.com/conversations/photoshop/photoshop-file-name-and-extension-highlight-w...

[Stephen Marsh]

Long standing issue for 1+ years or so, until Adobe fix it a script is the only workaround that I know of.