FUXA has an unauthenticated arbitrary tag value disclosure via /api/getTagValue

Summary

An authorization bypass in the /api/getTagValue endpoint allows unauthenticated access to tag values when the referenced script does not exist.

Details

The issue is caused by the combination of these code paths:

- server/api/apikeys/verify-api-or-token.js:45 sends requests without x-api-key to authJwt.verifyToken(req, res, next). - server/api/jwt-helper.js:46-64 creates a signed guest token when no x-access-token is provided: if (!token) { token = getGuestToken(); } and then populates req.userId / req.userGroups from that guest token. - server/api/command/index.js:76-105 exposes /api/getTagValue. - server/runtime/scripts/index.js:106-111 returns true when the referenced script does not exist: if (!script) { return true; }

As a result, an unauthenticated request reaches /api/getTagValue as guest, and the authorization check is bypassed because isAuthorisedByScriptName() returns true when sourceScriptName is omitted or does not match a real script. The endpoint then returns arbitrary tag values by ID.

PoC

Requests to /api/getTagValue without authentication could succeed when the authorization logic evaluated a non-existent sourceScriptName as authorized.