(1) What's wrong?: Recently, I have read info on turbowarp regarding scratch's vulnerabilities. Apparently, viruses (or some sort of harmful digital code) can impact your device simply by editing the project and going to costumes. Although this may not be exactly what the case is, it still poses a significant risk. Apparently, it relates to malicious SVG files able to corrupt or infect your computer in some way. I do not know the entire story, so PLEASE check turbowarp for further info on the situation.
(2) What this means: Scratch, at least the "see inside" feature is risking your safety. What you should do is avoid seeing inside on projects made by people who are unknown. You should also read the comments, as they could notify you of harmful structures in the project (do NOT rely on comments only) I cannot assure you that my projects are safe, but all projects before this are more likely to be safe. (A surge of inactivity may mean I have had something happen to my account. All credits go to turbowarp. STAY SAFE!