GHSA-9hc2-hjx8-q6pv: TidGi Desktop Remote Code Execution via Malicious TiddlyWiki Repository Import — Tiddler Startup Module Auto-Execution

TidGi Desktop through 0.13.0 contains a critical remote code execution vulnerability exploitable via a single Git repository import. The vulnerability leverages TiddlyWiki’s module system, which automatically discovers and executes JavaScript code embedded in .tid files placed in the wiki’s tiddlers/ directory:

1. Auto-loading of .tid files (src/services/wiki/wikiWorker/loadWikiTiddlersWithSubWikis.ts:59-92) — when TidGi boots a wiki workspace, loadWikiTiddlers reads all .tid files from the filesystem and adds them to the wiki store via wiki.addTiddlers().

2. Automatic module registration (node_modules/tiddlywiki/boot/boot.js:2564-2565) — defineTiddlerModules() iterates all tiddlers in the store. Any tiddler with a module-type field is passed to $tw.modules.define(), registering it as an executable module.

3. Automatic startup execution (node_modules/tiddlywiki/boot/boot.js:2572-2634) — all registered modules of type "startup" are collected and their exports.startup() function is called during the boot sequence. When no platforms restriction is set, doesTaskMatchPlatform() returns true, and the startup function executes with full Node.js require() access in the Wiki Worker process.

The full chain was verified on macOS with TiddlyWiki 5.4.0 and Node.js v26 — require('child_process').execSync() successfully executed arbitrary shell commands.