excalidraw is an open source virtual hand-drawn style whiteboard. A stored XSS vulnerability in Excalidraw's web embeddable component. This allows arbitrary JavaScript to be run in the context of the domain where the editor is hosted. There were two vectors. One rendering untrusted string as iframe's `srcdoc` without properly sanitizing against HTML injection. Second by improperly sanitizing against attribute HTML injection. This in conjunction with allowing `allow-same-origin` sandbox flag (necessary for several embeds) resulted in the XSS. This vulnerability is fixed in 0.17.6 and 0.16.4.