Nope, only add-ons from this source are from the xxx:
https://portal.otrs.com/external/download-center
That doesn't automatically mean they are well programmed or work flawless, but you should always check the source of the add-on.
It's just like any other add-on based software.
OTRS, however, does not have an official add-on store which is managed by the software vendor or the community, like Wordpress, Chrome/Firefox web store etc.
Sources, I'd consider pretty safe: 100% free: OPAR | free and commercial: xxx, Znuny, feature-addons, and us (Efflux).
But that's just based on my experience.
You should contact the vendor for this error.
Best regards
Emin