GHSA-7cqp-7cfv-6c3q: AVideo Meet plugin: anonymous-to-admin stored XSS via unescaped participant User-Agent in getMeetInfo.json.php Participants panel
SummaryThe Meet plugin stores the raw HTTP `User-Agent` header of every meeting participant and later renders it without output encoding in the meeting-management ("Participants") panel that the meeting host and site administrators open. An anonymous, unauthenticated attacker can join any public meeting while sending a `User-Agent` header containing an HTML payload. The payload is persisted in `meet_join_log.user_agent` and, when the host or an administrator opens the participant list, is injected verbatim into their DOM, executing attacker-controlled JavaScript in a privileged, authenticated session. This is a cross-privilege stored XSS: an anonymous visitor obtains script execution in the administrator's browser.Affected versions`WWBN/AVideo` at current `master` commit `e8d6119f3cb1b849149906efeb0a41fc024f59f8` (and prior releases shipping the same code path). Not patched at the time of this report.Privilege required**Writer (attacker):** unauthenticated / anonymous. Joining a public meeting requires no account and no password.**Victim (trigger):** the meeting host or any site administrator who opens the meeting's participant-management panel.Vulnerable code (file:line)The stored value is never sanitized on write, then echoed without encoding on read.Write path — `plugin/Meet/Objects/Meet_join_log.php:147`:Write path — `plugin/Meet/Objects/Meet_join_log.php:177`:`get_browser_name()` (`objects/functionsBrowser.php:239` and `:242`) returns the original-case `User-Agent` verbatim for any agent not matched to a known browser name:Only the lowercased match copy is used for classification; the returned string still contains the raw, original `$_SERVER['HTTP_USER_AGENT']`. Because the value bypasses AVideo's object-setter sanitization layer (unlike `Meet_schedule::setTopic()`, which calls `xss_esc()`), the raw bytes reach the database unchanged.Read path — `plugin/Meet/getMeetInfo.json.php:71`:`$value['user_agent']` is concatenated into the HTML with no `htmlspecialchars()`. The reader endpoint is gated by `Meet_schedule::canManageSchedule()` (site admin OR the schedule owner), so the value is rendered in a privileged context.How input reaches the sinkThe join that records the log is reachable anonymously through `plugin/Meet/iframe.php:11` and `:17`:For a public meeting (`public = 2`), `Meet::validatePassword()` returns `true` for an anonymous request (no password set), so `Meet_join_log::log()` runs and stores the attacker's `User-Agent`. On the read side, the host/admin opens the participant modal, whose JavaScript fetches `getMeetInfo.json.php` and injects the response with jQuery `.html()` in `plugin/Meet/meet_scheduled.php:266`:`.html(response.html)` parses and inserts the attacker-controlled markup, so the injected `onerror` handler executes in the host/admin DOM.Proof of concept — end-to-end reproduction (against pinned version)Deployed against the project's official Docker stack (php8.5/apache2.4 + mariadb), pinned commit `e8d6119f3cb1b849149906efeb0a41fc024f59f8`. `<TARGET>` is the deployed host.The JSON `html` field contains the payload **unescaped**:When the admin opens the participant modal in a browser, jQuery `.html(response.html)` injects this markup and the `onerror` handler executes in the admin's authenticated session, printing `document.domain`.**Negative control:** joining with a benign browser `User-Agent` (`Mozilla/5.0 (Windows NT 10.0) Chrome/120.0 Safari/537.36`) causes `get_browser_name()` to return `Chrome`, which renders as plain text `<small class="text-muted">Chrome</small>` with no markup injection.ImpactCross-privilege stored XSS: an unauthenticated, anonymous visitor achieves JavaScript execution in the meeting host's and site administrator's authenticated browser sessions.Full account-takeover surface: theft of the admin session, CSRF-token exfiltration, and arbitrary authenticated actions (user and permission changes, plugin configuration) performed as the administrator.The payload persists in the database and fires for every privileged user who reviews the participant list of the affected meeting.Suggested fixEncode the stored value at the sink in `plugin/Meet/getMeetInfo.json.php:71`:Defense in depth: sanitize the value on write in `Meet_join_log::setUser_agent()`, mirroring the setter-layer encoding used by `Meet_schedule::setTopic()` (`xss_esc()`), so any other current or future reader of `meet_join_log.user_agent` is also protected.Fix PRA fix is provided on the advisory's private temporary fork: `WWBN/AVideo-ghsa-7cqp-7cfv-6c3q#1` (encodes the participant `User-Agent` at the sink with `htmlspecialchars($value['user_agent'], ENT_QUOTES, 'UTF-8')`).CreditReported by tonghuaroot.
CVSS v4.0: 5.4