SiYuan is an open-source personal knowledge management system. Prior to 3.7.0, he tooltip mouseover handler in app/src/block/popover.ts reads aria-label via getAttribute and passes it through decodeURIComponent before assigning to messageElement.innerHTML in app/src/dialog/tooltip.ts:41. The encoder used at the producer side, escapeAriaLabel in app/src/util/escape.ts:19-25, only handles HTML special characters (", ', <, literal &lt;), it leaves %XX URL-escapes untouched.

So a doc title containing %3Cimg src=x onerror=...%3E round-trips through escapeAriaLabel and the HTML attribute layer unmodified. Then decodeURIComponent on the consumer side converts %3C to a literal < character (a real <, NOT a character reference). When that string is assigned to innerHTML, the HTML5 tokenizer enters TagOpenState on the literal <, parses the <img> element, and the onerror handler fires.

Because the renderer runs with nodeIntegration: true, contextIsolation: false, webSecurity: false (app/electron/main.js:407-411), require('child_process') is reachable from the injected handler, escalating to arbitrary code execution.This vulnerability is fixed in 3.7.0.