Zoom's Linux client reads everything written to the X11 clipboard, not just what you paste.

Simon Tatham posted on September 12 that the client proactively requests clipboard contents on every selection change, so text you select anywhere on the desktop gets pulled into Zoom's process. 347 points on HN. X11 hands the current selection to any client that asks, so the mitigations are Wayland or the browser client. If you copy credentials during a call, you've already sent them.