My first guess is that this is related to Cross-Site Request Forgery "CSRF" protection that went into effect when we upgraded to version 18.3. Below, I have pasted an explanation from Josh Eckels. Sorry for not doing a better job of announcing this to PanoramaWeb.org users ahead of the upgrade.
Short version: Please upgrade to recent versions of Skyline and AutoQC to make sure they will be compatible with new versions of LabKey Server and Panorama.
As part of our effort to make sure that LabKey Server and Panorama protect against potential security threats, we've been gradually getting stricter about how we validate requests against an attack called Cross-Site Request Forgery (CSRF). The Skyline team has been working to make sure that it includes the required information to validate the requests it makes when uploading data to Panorama.
When you upgrade to LabKey Server version 18.3, it will automatically do more stringent checks than old versions did. You'll want to be sure you're using versions of Skyline or AutoQC that include the right information in their requests. The minimum versions that do are:
Skyline: version 4.2
Skyline-daily: version 22.214.171.12451
AutoQC Loader - version 126.96.36.19902
In version 18.3, LabKey administrators can relax the validation in a way that will be compatible with older Skyline and AutoQC releases. In 19.1, this will no longer be possible.
If you're not running with a compatible combination, you'll see errors when uploading to Panorama from Skyline, and there will be a message in the labkey.log file about suspicious request(s).
For more details, please see the documentation here:
Please let me know if you have any questions or concerns. Hopefully most everyone has already upgraded to the latest Skyline and AutoQC versions.