Hi @hrhnick
Before attempting to work around this certificate issue, I would head over to Toshiba to see if they have an updated package you can download for these drivers. Package installers from known commercial developers have signed certificates in them that are trusted and the Apple installer can check on. If the embedded cert has expired or been revoked for any reason, it will see this and not allow the installation to take place unless you choose to override it. This is a security precaution, to prevent you from installing a potentially compromised or damaged installer package on your Mac.
So, first check to see if Toshiba has corrected this with a new pkg install. If there is one, download it, upload to your Jamf instance and swap the old one out for the new one and try it again.
If there is no new package, I would try to contact Toshiba support on it to see if they are even aware of a bad cert in their package and if they plan on releasing a new one. If that doesn't work, then the only recourse will be to do some workarounds for this one package. While I don't really recommend this, if you are for sure certain this package installer is legit and was not causing any issues before, you can do the following.
Copy the installer package into a new folder in /private/tmp/, such as /private/tmp/Toshiba/ or something like that.
Open Composer and drag the new folder from tmp that has the pkg installer in it to the sidebar to create a new package source. Composer will copy it in and the contents.
Adjust any permissions on the package as necessary. It's usually fine to copy down the permissions on /tmp/ to the folders below it to match.
Open the package disclosure triangle in the sidebar to reveal the Scripts section. Right/Control click on Scripts and choose Add Shell Script > PostInstall
Now in that new PostInstall script, add something like this to it.
#!/bin/sh
PKG="/private/tmp/Toshiba/PackageName.pkg ## Adjust "PackageName.pkg" to match the actual name. Make sure to include the ".pkg" extension
## Install the pkg with the -allowUntrusted flag
/usr/sbin/installer -pkg "$PKG" -tgt / -allowUntrusted
Now build this out as a new PKG installer, upload into Jamf and replace the other installer in your policy with this new one and try having the policies run again.
The above script will use the installer command to install the pkg inside the folder using the mentioned -allowUntrusted flag, and it should install, hopefully. It's been a while since I've needed to use something like this, so I can't be 100% sure how current OS versions will work with it, but, as of Mojave, -allowUntrusted is still a valid flag in the man page for installer, so it should work.
