I’m not completely updated on the events but as I understand the original add-on changed ownership and was sold to a unknown group of Turkish developers against whom the claim of injecting malware is. The Chrome and Edge version is affected but not the Firefox one because the same add-on is maintained by another person for Firefox: https://github.com/LiCybora/NanoDefenderFirefox/blob/master/README.MD and is changing name to distance itself from upstream https://github.com/LiCybora/NanoDefenderFirefox/issues/188. The person making the analysis on the linked thread gorhill is the developer of the popular add-ons uBlock Origin, uMatrix etc.
How was nano defender different from ublock origin anyway? (Before this malware injection.)
It’s listed here : https://github.com/NanoAdblocker/NanoCore#notable-changes Mainly small tweaks directly based on uBlock origin, and direct support to Nano Defender, which is, a module for uBlock origin (And forks of it) to bypass some anti-adblock counter-measures.