Hi Ankur,
We had such an issue reported by users of specific region and we were not able to replicate the issue at our end.
However the resolution provided us to keep hold on Ctrl button while clicking on the attachment link. After clicking it asked for two options either to Open the document or to Save it.
By holding Ctrl key users were able to Open/ Save the attachment.
Please check if this works fine for you as well.
Regards,
Anil Bansal