Zulip 4.9 release notes | WinterFlow.io

CVE-2021-43799: Remote execution of code involving RabbitMQ.
Closed access to RabbitMQ port 25672; initial installs tried to close this port, but failed to restart RabbitMQ for the configuration.
Removed the rabbitmq.nodename configuration in zulip.conf; all RabbitMQ instances will be reconfigured to have a nodename of zulip@localhost. You can remove this setting from your zulip.conf configuration file, if it exists.
Added missing support for the Camo image proxy in the Docker image. This resolves a longstanding issue with image previews, if enabled, appearing as broken images for Docker-based installs.
Fixed a bug which allowed a user to edit a message to add a wildcard mention when they did not have permissions to send such messages originally.
Fixed a bug in the tool that corrects database corruption caused by updating the operating system hosting PostgreSQL, which previously omitted some indexes from its verification. If you updated the operating system of your Zulip instance from Ubuntu 18.04 to 20.04, or from Debian Stretch to Debian Buster, you should run the tool, even if you did so previously; full details and instructions are available in the previous blog post.
Began routing requests from the Camo image proxy through a non-Smokescreen proxy, if one is configured; because Camo includes logic to deny access to private subnets, routing its requests through Smokescreen is generally not necessary.
Fixed a bug where changing the Camo secret required running zulip-puppet-apply.
Fixed scripts/setup/compare-settings-to-template to be able to run from any directory.
Switched Let’s Encrypt renewal to use its own timer, rather than our custom cron job. This fixes a bug where occasionally nginx would not reload after getting an updated certificate.
Updated documentation and tooling to note that installs using upgrade-zulip-from-git require 3 GB of RAM, or 2 GB and at least 1 GB of swap.