As stewards of the Eclipse Marketplace, the Eclispe Foundation is responsible for providing a safe place for the Eclipse IDE users to download their plugins. While the Eclipse Marketplace does not host or transmit the plugins bits, it provides links to (p2) repositories containing them. Until today, there was no restriction on those links.
Beginning December 15, 2022, the Eclipse Marketplace will no longer support links to repositories over plain HTTP. The goal is to protect users of the Eclipse Marketplace from the main risk of plain HTTP links: man-in-the-middle (MITM) attacks.