A new developer portal version has just been released. It addresses security vulnerabilities introduced in version 2.7.0.
If you're using the built-in (managed) developer portal, your portal will be automatically upgraded within two weeks. Make sure to republish it to upgrade the published portal.
If you're using a self-hosted developer portal, you need to merge the source code changes and republish and redeploy your portal manually.
Detailed release notes are available in the developer portal repository.