Vim is an open source, command line text editor. From 9.2.0469 until 9.2.0843, popup_mark_opacity_zindex() in src/popupwin.c can use a negative w_winrow for a text-property-anchored popup with clipwindow and opacity, indexing before the screen array instead of accounting for w_popup_topoff and causing an out-of-bounds read and conditional write. This issue is fixed in version 9.2.0843.