This, as you can probably tell, is a virus. The cause of it is one of your (or your friend’s) plugins. Will you send a screenshot of the plugins you use?
Even if you only used GapFill, plugins can run by themselves (used or not). GapFill is not a virus so it is one of the other plugins owned by any of you.
Part Counter
Archimedes
Model Resize --Though make sure it is from the original developer because I don't know who it is.
Beveler
AutoScale --I might be wrong but I am pretty sure it is safe
Load Character
Moon Animator
3D Text --Once again, make sure its from original dev
Part to Terrain
F3X Building Tools
Gap Fill --And the other plugins by Stravant
This is the wrong category, but that’s alright… This is a very blatant virus from either a plug-in you have, or a free model that you used. Make sure all the plugins you use are made by trusted people and not some random group with a name like R0BLOXPLUGINS… Also checking comments of the groups that are linked with plugins are helpful as there are always people saying that they are backdoor viruses. Anyways, I hope I helped,