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

• npm tidgi: <= 0.13.0 (no fix yet)

Description 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 `$tw.modules.define()`, registering it as an executable module. 3. Automatic startup execution (`node_modules/tiddlywiki/boot/boot.js:2572-2634`) — all registered modules of type `"startup"` are collected and their `exports.startup()` function is called during the boot sequence. When no `platforms` restriction is set, `doesTaskMatchPlatform()` returns `true`, and the startup function executes with full Node.js `require()` access in the Wiki Worker process. The full chain was verified on macOS with TiddlyWiki 5.4.0 and Node.js v26 — `require('child_process').execSync()` successfully executed arbitrary shell commands. Affected Product • Product: TidGi Desktop • Vendor: Lin Onetwo (https://github.com/tiddly-gittly) • Repository: https://github.com/tiddly-gittly/TidGi-Desktop • Affected Versions: 0.13.0 (latest release) • Components: `src/services/wiki/wikiWorker/loadWikiTiddlersWithSubWikis.ts` (tiddler loading), `src/services/wiki/wikiWorker/startNodeJSWiki.ts` (wiki boot), `node_modules/tiddlywiki/boot/boot.js` (TiddlyWiki core — `defineTiddlerModules`, startup dispatch) • Package: tidgi (npm) Vulnerability Details Root Cause 1 — `.tid` Files Auto-Loaded Before Module Processing File: `src/services/wiki/wikiWorker/loadWikiTiddlersWithSubWikis.ts:59-92` ```typescript const tiddlerFiles = wikiInstance.loadTiddlersFromPath(subWikiTiddlersPath); for (const tiddlerFile of tiddlerFiles) { // Register file info for filesystem adaptor // ... // Add tiddlers to wiki wikiInstance.wiki.addTiddlers(tiddlerFile.tiddlers); // ← Line 92 } ``` File: `src/services/wiki/wikiWorker/startNodeJSWiki.ts:256` ```typescript wikiInstance.boot.startup({ bootPath: TIDDLY_WIKI_BOOT_PATH }); ``` This triggers `$tw.boot.startup()`, which internally calls `loadStartup()` → `loadTiddlersNode()` → `$tw.loadWikiTiddlers($tw.boot.wikiPath)` (boot.js:2381). TidGi overrides `loadWikiTiddlers` at startNodeJSWiki.ts:123 to intercept and inject sub-wiki tiddlers, but the original function still loads all `.tid` files from the main wiki's `tiddlers/` directory. Root Cause 2 — Automatic Module Registration via `module-type` Field File: `node_modules/tiddlywiki/boot/boot.js:1514-1534` — `defineTiddlerModules()` ```javascript $tw.Wiki.prototype.defineTiddlerModules = function() { this.each(function(tiddler,title) { if(tiddler.hasField("module-type") && (!tiddler.hasField("draft.of"))) { switch(tiddler.fields.type) { case "application/javascript": $tw.modules.define( tiddler.fields.title, // "$:/plugins/poc/startup.js" tiddler.fields["module-type"], // "startup" tiddler.fields.text // attacker's JS code ); break; } } }); }; ``` This function is called during `execStartup()` (boot.js:2565), after `loadStartup()` has already loaded all `.tid` files into the wiki store. Any tiddler with `module-type: startup` and `type: application/javascript` is automatically registered as an executable module. Root Cause 3 — Automatic Startup Execution with Full Node.js Access File: `node_modules/tiddlywiki/boot/boot.js:2572-2576` — Collecting startup modules ```javascript $tw.boot.remainingStartupModules = []; $tw.modules.forEachModuleOfType("startup", function(title, module) { if(module.startup) { $tw.boot.remainingStartupModules.push(module); // ← attacker's module collected } }); ``` File: `node_modules/tiddlywiki/boot/boot.js:2631-2634` — Executing startup ```javascript if(!$tw.utils.hop(task,"synchronous") || task.synchronous) { const thenable = task.startup(); // ← exports.startup() called ``` File: `node_modules/tiddlywiki/boot/boot.js:2658-2677` — Platform check (passes without explicit `platforms`) ```javascript $tw.boot.doesTaskMatchPlatform = function(taskModule) { var platforms = taskModule.platforms; if(platforms) { // ... check each platform ... return false; // ← only rejects if platforms is explicitly set } return true; // ← no platforms field → passes unconditionally }; ``` Complete Boot Sequence (verified against TiddlyWiki 5.4.0) ``` $tw.boot.startup() // boot.js:2589 ├── initStartup() // boot.js:2393 ├── loadStartup() // boot.js:2538 │ └── loadTiddlersNode() // boot.js:2356 │ └── $tw.loadWikiTiddlers(wikiPath) // boot.js:2381 │ └── wiki.addTiddlers(...) // loads .tid files into store └── execStartup() // boot.js:2553 ├── defineShadowModules() // boot.js:2564 ├── defineTiddlerModules() // boot.js:2565 ← registers attacker's module ├── forEachModuleOfType("startup", ...) // boot.js:2572 ← collects startup modules └── executeNextStartupTask() // boot.js:2611 └── task.startup() // boot.js:2634 ← exports.startup() executes ``` Exploitation Conditions • No authentication required — importing a wiki is a standard feature • Only user interaction: click "Add Workspace" → select folder/URL → confirm Complete Attack Flow ``` ┌──────────────────────────────────────────────────────────────┐ │ Step 1: Attacker creates a malicious TiddlyWiki repository │ ├──────────────────────────────────────────────────────────────┤ │ tiddlers/$__plugins__poc__startup.js.tid: │ │ │ │ title: $:/plugins/poc/startup.js │ │ type: application/javascript │ │ module-type: startup │ │ │ │ exports.startup = function() { │ │ require('child_process').execSync('calc'); │ │ }; │ │ │ │ + tiddlywiki.info + any other wiki files │ └──────────────────────────────────────────────────────────────┘ ↓ ┌──────────────────────────────────────────────────────────────┐ │ Step 2: Victim imports the repository into TidGi Desktop │ ├──────────────────────────────────────────────────────────────┤ │ Add Workspace → Clone Git Repository / Open Local Folder │ │ → TidGi boots the wiki │ └──────────────────────────────────────────────────────────────┘ ↓ ┌──────────────────────────────────────────────────────────────┐ │ Step 3: RCE — startup module auto-executes in Node.js Worker │ ├──────────────────────────────────────────────────────────────┤ │ loadWikiTiddlers loads .tid file → wiki.addTiddlers() │ │ boot.startup() → execStartup() │ │ defi…