memono Notepad 4.2 contains a denial of service vulnerability that allows attackers to crash the application by pasting excessively long character buffers into note fields. Attackers can generate a payload containing 350000 repeated characters and paste it twice into a new note to trigger an application crash on iOS devices.
https://www.vulncheck.com/advisories/memono-notepad-denial-of-service-via-buffer-overflow