In Mars M6 a fix  went into Equinox
that allows an Equinox extension hook implementation to return resource
URLs that use a different protocol than the built-in bundleresource protocol.
For example, Virgo has the need to return the VM built-in jar or
file URLs in some scenarios. While doing the final testing of the
Mars release candidates I found this change causes a breaking change in
the behavior for resource URL lookups when equinox hooks are present which
want to augment the content of the bundle resources . This must
be fixed for Mars in my opinion. But in order to fix this any equinox
extension hooks that want to change the protocol used for resource URLs
will need to override a different method. For more information please
Unfortunately this change is not available
in RC3, but this late change impacts a very small number of projects. I
really only know of it impacting Virgo. Please comment in the bug
 if you have concerns.