GHSA-ghcv-22jf-vfxm: AVideo has an Incomplete Fix for YPTSocket autoEvalCodeOnHTML Strip: Unauthenticated Cross-User JavaScript Execution via `$msg['json']` Relay Bypass
SummaryThe server-side mitigation for the YPTSocket `autoEvalCodeOnHTML` eval sink (prior advisory GHSA-gph2-j4c9-vhhr, commit `c08694bf6`) only strips the payload when it sits under `$json['msg']`, but the relay function `msgToResourceId()` selects the outbound message from `$msg['json']` *before* `$msg['msg']`. An unauthenticated attacker can obtain a WebSocket token from `plugin/YPTSocket/getWebSocket.json.php`, connect to the WebSocket server, and send a message with `autoEvalCodeOnHTML` nested under a top-level `json` field — the strip branch is skipped, the relay delivers the payload verbatim to any logged-in user identified by `to_users_id`, and the client script runs it through `eval()`.DetailsEntry point (unauthenticated)`plugin/YPTSocket/getWebSocket.json.php` (lines 1–21) issues a valid WebSocket token to any caller, with no authentication or CSRF check:`getEncryptedInfo()` defaults to `sentFrom = 'browser'` and a non-CLI flag (`plugin/YPTSocket/functions.php:3-47`), so a token minted for an anonymous browser client will cause the strip branch below to run — which is exactly what we want to audit.Incomplete strip (the fix from commit c08694bf6)`plugin/YPTSocket/Message.php:236-247`:If the incoming `$json['msg']` is a scalar (e.g. the string `"x"`), `is_array(...)` is false and the strip is skipped entirely. Any eval-able content that lives elsewhere in `$json` passes through untouched. The same flawed check exists in `plugin/YPTSocket/MessageSQLiteV2.php:285-293`.Relay preference picks the untouched field`plugin/YPTSocket/Message.php:316-322` (and the mirror at `MessageSQLiteV2.php:396-402`):An attacker payload shaped as `{"msg": "x", "json": {"autoEvalCodeOnHTML": "<js>"}, "to_users_id": <victim>}` therefore:Passes `switch ($json->msg)` into the `default` case (Message.php:211, 228).`msgToArray($json)` converts to array. The strip branch enters because `sentFrom === 'browser'`, but `is_array("x")` is false and the strip is skipped.Routing lands on `msgToUsers_id($json, $json['to_users_id'])` (Message.php:253), which for each matching resource calls `msgToResourceId($msg, $resourceId)` (Message.php:379).In `msgToResourceId`, `!empty($msg['json'])` is true, so `$obj['msg']` becomes `{"autoEvalCodeOnHTML": "<js>"}` (Message.php:316-317).The `shouldPropagateInfo()` check at Message.php:287-289 only logs — it does not return — so delivery proceeds regardless.Client-side sink`plugin/YPTSocket/script.js:573-575`:Any logged-in user with an active browser tab runs the attacker-supplied JavaScript in the origin of the AVideo installation.Routing to any user`msgToUsers_id()` (Message.php:362-389) looks up `to_users_id` against `$this->clientsUsersId` and relays to every resource belonging to that user. Because `to_users_id` comes straight from attacker input, any currently connected user (regular or admin) can be targeted. Active users_id values can be enumerated via the existing `getClientsList` request handled at Message.php:219-224 using the same unauthenticated token.PoCStep 1 — mint an unauthenticated WebSocket token:Step 2 — connect and send the crafted message:Expected result: the victim's tab receives `{"type":"DEFAULT_MESSAGE","msg":{"autoEvalCodeOnHTML":"alert(...)"}, ...}` and executes the JavaScript via `eval()`.Optional Step 0 — enumerate active users (using the same token):Impact**Unauthenticated XSS / arbitrary JS execution in any logged-in user's browser session.** The victim only needs a tab open on the site — no click, no link, no CSRF.**Same-origin compromise:** the attacker's JS runs in the target origin, so it can read DOM/tokens, make authenticated XHR calls on the victim's behalf, and exfiltrate session data.**Privilege escalation when an admin is targeted:** arbitrary admin-panel actions via same-origin XHR — account takeover, plugin configuration changes, file uploads, etc.**Mass exploitation feasible:** `getClientsList` (also reachable with the anonymous token) enumerates active `users_id` values, and the attacker can iterate `to_users_id` across all of them.This is an incomplete fix for GHSA-gph2-j4c9-vhhr — deployments that patched to commit `c08694bf6` remain exploitable.Recommended FixScrub `autoEvalCodeOnHTML` from **every** outbound carrier the relay may choose, not only from `$json['msg']`. Patch both `plugin/YPTSocket/Message.php` and `plugin/YPTSocket/MessageSQLiteV2.php`. For example, replace the current strip in `onMessage()`:Additionally, harden the relay itself in `msgToResourceId()` (both files) so future regressions cannot reintroduce the sink — walk the chosen `$obj['msg']` recursively and unset `autoEvalCodeOnHTML` whenever the message originated from a non-PHP, non-CLI client. As defense in depth, remove or gate the client-side `eval(json.msg.autoEvalCodeOnHTML)` at `plugin/YPTSocket/script.js:573-575` behind a server-signed field rather than a plain JSON key.
CVSS v3.1: 7.2