Hi Leon,
This appears to be a bug - the file extension should not be removed when you download the file. We have logged a ticket to fix this.
In the meantime, there is a workaround. Please follow these steps:
1. Download the attached html file
2. Open the file using a text editor or anything that edits HTML. Change the href="sample_sheet.xlsx" reference to match your file name (e.g. href="mydocument.docx"). Save your change.
![](https://cdn.screencast.com/uploads/g000302p1Wt2JuG8eUtlkfnTfOSbI/09.12.2023-12.51.png?sv=2022-11-02&st=2023-09-12T11%3A52%3A32Z&se=2023-09-13T11%3A52%3A32Z&sr=b&sp=r&sig=woHvI1lkQKvJU02cOdkJN1KXm7jvevcHDKHDTngCvtc%3D)
3. Create a Zip containing both the html and your file. The name of the zip file doesn't matter.
![](https://cdn.screencast.com/uploads/g000302Cp6XFB8KzHomTET4LOy4A9/09.12.2023-12.51.png?sv=2022-11-02&st=2023-09-12T11%3A53%3A16Z&se=2023-09-13T11%3A53%3A16Z&sr=b&sp=r&sig=Cg5I25%2BUEEHp6bD%2BEaKKPMAfeu6gNwDDHL1auK37xdk%3D)
4. In SmartBuilder, add an asset object and in the Asset property, select the zip file.
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5. In the Select File window, type "download.html". Note that the input field border is not visible in dark mode, but you can type into it (We will fix this). Click OK.
![](https://cdn.screencast.com/uploads/g000302lntrUesNHuANGIo8rS38n5/09.12.2023-12.54.png?sv=2022-11-02&st=2023-09-12T11%3A56%3A37Z&se=2023-09-13T11%3A56%3A37Z&sr=b&sp=r&sig=BtEbN9c4McmghWw%2FBngrfqWD0Amx50uTv0%2BhVevOcMg%3D)
6. Set up your action to open the asset. For example: Button1.onClick > Asset1.open
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Let us know if that works for you!