Could not open MS office files inside a WPF application using WebView2

Hi,

We have an internal WPF application that uses WebView2 to render an internal web application, the web application returns a MS word file in docx, doc, csv, rtf and pdf formats (with content-disposition:inline; filename header), Prior to 7th April 2025 the WebView2 use to open the files within the WebView2. But after 7th April it just downloads the docx, doc, csv, rtf files in the downloads folder but doesn't display anything on the WebView, however, PDF files still opens in the Webview. Is their any change in the runtime, or is this feature is dropped ?

I also see that the file extension after the download is .tmp, which is similar to the issue pointed by this Q&A https://learn.microsoft.com/en-us/answers/questions/2261245/file-download-issue-in-webview2-new-windows-after, I am not sure if both the issues are related. The downloaded file can be opened If I rename the file to the correct extension and double click it.

Additionally, I would like to report this issue through the appropriate support channels. If there is a preferred method or platform for reporting such runtime issues (e.g., GitHub repository, Microsoft Q&A, etc.), please advise.

Details:

OS: Win10

WebView2 runtime version: 135.0.3179.98

WebView2 library version: 1.0.1108.44

Date issue reported: 7th April 2025