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.