What is doublelist upgrade?

As an AI language model, I don't have access to current and specific information about Doublelist upgrade. However, based on general knowledge about upgrades, it is likely that Doublelist upgrade refers to an improvement or update to the Doublelist platform. This upgrade could include new features, enhanced security measures, improved user interface, or bug fixes. Upgrading the platform can provide a better user experience and increase the platform's functionality and overall performance.