How to populate the publisher field for an Excel VSTO addin

Question

How to populate the publisher field for an Excel VSTO addin

Burke, Denis 0

I publish a VSTO application-level addin for Excel. It is written in c# with VS Enterprise 2022. We install the addin by creating an MSI installer using WIX. I sign all DLLs, the application manifest, and the MSI installer. All files appear properly signed and publicly valid. The application installs fine and runs fine. The only issue I have is when I look at the add by going to Excel and FILE...OPTIONS...ADD-INS and select my addin: it always shows <None> as the Publisher. This is the case on every machine I have tested on (>10 machines). This would be a cosmetic issue, but I have one user who installs the app and when trying to run it sees the message that he can only run addins from trusted publishers. I know this is a policy from his organization, so I would like to comply and present a Publisher that they could safely trust.

Any ideas? Please let me know if there is any more info that would be helpful.

Thanks.

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Answer 1

Hi Denis,

Greatly appreciate your detailed sharing.

This is likely because the "publicly valid code-signing certificate" and "Trusted Publisher in Office policy" are not the same.

Refer to Registry entries for VSTO Add-ins - Visual Studio (Windows) | Microsoft Learn, for a VSTO application-level add-in deployed by MSI/WiX, Excel discovers the add-in from registry values such as Description, FriendlyName, LoadBehavior, and Manifest. Based on the documentation, the registry entries do not include a Publisher value that you can populate for that Add-ins screen.

About the user’s block, it is probably because their organization has enabled “Require that application add-ins are signed by Trusted Publisher”, and your signing certificate has not been added to the user’s or machine’s Trusted Publishers certificate store. A certificate can chain to a public CA and still not be in the Office/Windows Trusted Publishers list.

These are what I know about your situation so far. That said, for you to receive the best possible assistance regarding this issue, I recommend you sharing your situation in the Excel | Microsoft Community Hub. This forum is dedicated to Excel and is actively monitored by power users, Microsoft partners, and engineers who can provide step-by-step guidance and share best practices.

I apologize for redirecting you to another community, as I may not have the necessary skills and experience to solve your Excel issue. That said, this is the most effective help I can provide from my position so you can receive the most correct, specialized support for this situation.

Thank you for your understanding and I truly hope everything will be resolved soon.

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Burke, Denis 0 Reputation points

2026-08-01T02:25:30.3066667+00:00

Many thanks for the great reply. However it does not lead to a way to populate the Publisher field for an Excel addin, which is my core problem. As for what forum to post this question in: it is an issue affecting Excel but I suspect the issue may be in how I developed the solution or signed parts of the solution, so I am not sure if I need help with Visual Studio or Excel.
Hendrix 970 Reputation points Independent Advisor

2026-08-03T23:43:26.7233333+00:00

Hi Denis,

Greatly appreciate your response.

If that's the case, the Tech Community Hub is still the most appropriate forum for this add-in development problem since there are many users with years of experience and in-depth knowledge actively monitor that forum. If the issue is not mainly about Excel, you can change the tag from Excel to the one that most relevant to your issue so you will receive the best possible assistance.

Thank you for your patience and understanding. Wishing you a great day ahead.