Upgrading from 1.8 — nothing you have to do. The new integrations are off until you turn them on. The update check is on: at startup it looks online for a newer release, sending only the plugin and Minecraft versions, and update-check: false turns it off. With same-world-only on, carts, mobs, items and arrows now stay in their own world too. Coming from 1.7? 1.8.0's notes still apply. Installing for the first time? Drop the jar in and start.

• WorldGuard regions can refuse gates: wormhole-build and wormhole-use flags stop gates being built or used in a region. Set worldguard-enabled: true and restart.
• Gates, rings, public beam destinations and mirrors on a Dynmap web map, each as its own layer. Set dynmap-enabled: true. On 1.21.11 use Dynmap 3.8; there is no Dynmap for 26.x yet.
• A newer release is announced at startup, in the console and to ops as they join. Nothing is downloaded.
• same-world-only now keeps carts, mobs, items and arrows in their own world too, and ten settings that waited for a restart now apply at once from /wormhole config.
• Gate fixes: thrown and dispensed items go through an open gate, tipped arrows keep their effect, and a cart stops at the face of a shut iris instead of rolling into it.

Full changelog