Contact
Found a problem, or a file that did not come out right? Say so.
Before you write
Please do not send the file that caused a problem unless you are asked to, and never send one with private contents. A description is usually enough: what kind of file, which tool, which browser, and what you saw. If a tool showed “Copy error details”, paste that text in.
Security reports
If you find a way for a file, or anything about a file, to leave the device, that is the most serious bug this site can have. Write with “Security” in the subject line. Reports like this are answered first. The fix is published, and you are credited if you want to be.