Why are cookies unrecognized when a link is clicked from an external source (i.e. Excel, Word, etc…)

Question

I noticed that when a link is clicked externally from the web browser, such as from Excel or Word, that my session cookie is initially unrecognized, even if the link opens u

Answer 1

Here is an example of the fix using a dotnet core middleware:

public class MicrosoftOfficeLinksHandlingMiddleware
{
    private static readonly Regex MsUserAgentsRegex = new Regex(@"[^\w](Word|Excel|PowerPoint|ms-office)([^\w]|\z)");
    private readonly RequestDelegate _next;

    public MicrosoftOfficeLinksHandlingMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task Invoke(HttpContext context)
    {
        string userAgent = context.Request.Headers["User-Agent"].FirstOrDefault();

        if (userAgent != null && MsUserAgentsRegex.IsMatch(userAgent))
        {
            // just return an empty response to the office agent
            return;
        }

        await _next(context);
    }
}