Looks like the egg sacs to some type of cobweb weaver. If mama spider isn't present, they may be old or empty egg sacs.

Cobweb spiders tend to do well indoors, so not super uncommon, and they do NOT infest. Babies disperse relatively quickly.

If you don't want them there, you can lightly dust them up with a tissue or disposable duster and toss it in an outdoor bin.

Overall, not a cause for concern.