Windows Update says there’s a critical update for Windows. Critical to me implies that it’s absolutely vital to the smooth running of your PC. The description of the update left me wondering so I took a couple of screenshots of character map before and after the update.
The update description says “This item updates the Bookshelf Symbol 7 font included in some Microsoft products. The font has been found to contain unacceptable symbols.”

What’s wrong with it? Well, here’s an image showing the two affected rows of characters (from character map). The top two rows are from the original file, and the lower two rows from the post-update file. Spot the differences.

Answer: the two swastika characters and the Jewish star.