Blocks shorts.

uBlock filters use a modified form of CSS selectors to determine what parts of a page to hide.

If you know vaguely how CSS selectors work you can infer that the filter definition is matching on youtube.com and is finding an element whose title property is shorts - so it seems to be doing an appropriate thing.

The important part is that uBlock filters are not executable; you can’t inject a malicious executable through one, as they are simply patterns which describe what parts of a page should be hidden, and hiding content is all they can do.

The worst that a filter could do is hide something that shouldn’t be hidden.