The company I work for is developing an enterprise platform with file storage support. Part of the package is supporting WebDAV, which is implemented with sabre/dav. We support only Basic authentication right now.

Recently some of our clients reported that they’re unable to edit files over WebDAV. After some digging we found out that the issue appears only in the most recent versions of Office. More precisely, upgrading from 16.81 to 16.84 causes the new behaviour.

The issue is that instead of sending Authorization: Basic XXX Word now sends Authorization: Bearer (empty). It would be understandable if they completely disabled support for basic auth (as Microsoft apparently did in the latest Windows versions?), but the prompt to enter login/password still appears, the credentials are just never sent over.

Is there any way to address this issue except implementing support for another auth scheme?