Word Addin content is blocked because it isn't signed by a valid certificate when being IIS hosted in a website having a (*) wildcard certificate.

[cebrotea]

Word addin not loading when is hosted in a website that has a wildcard certificate *( Issued to: .domain.com)
Changing the website certificate to a named certificate (Issued to: machineName.domain.com) fixes the problem.

Your Environment

• Platform [PC desktop, Mac, iOS, Office on the web]: PC
• Host [Excel, Word, PowerPoint, etc.]: WORD
• Office version number: 2108 (Microsoft Word for Microsoft 365 MSO (16.0.14326.20850) 64 bit)
• Operating System: Windows 10 Pro 10.0.19044 Build 19044
• Browser (if using Office on the web): ______

Expected behavior

The addin should load no matter if the certificate is issued as a wildcard certificate

Current behavior

The addin cannot be loaded and it shows the following message: The content is blocked because it isn't signed by a valid certificate

Steps to reproduce

1. Create an IIS website that has a wildcard certificate ( *( Issued to: .domain.com) )
2. Deploy the addin files in the website location
3. Open word and try to open a taskpane that points to the addin

Context

Hosting the office js addin in a SAAS Environment is not possible because of this issue

Useful logs

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[samantharamon]

Thank you for reporting this, @cebrotea. @grangeryy, could you please assist with this? Thank you.

[cebrotea]

looks like I will close this one as not reproducible for now. It is reproduced when using self-signed wildcard certificates. Thank you.