ArcadeDB: Cross-database authorization bypass and unsecured newly-created databases

ArcadeDB is a Multi-Model DBMS. Starting in version 21.10.1 and prior to version 26.4.2, authenticated users and API tokens scoped to a specific database could read, write, and mutate schema on any other database on the same server. Two distinct defects contributed: (1) ServerSecurityUser.getDatabaseUser() returned a DB user with an uninitialized fileAccessMap, which requestAccessOnFile treated as allow-all; (2) ArcadeDBServer.createDatabase() omitted factory.setSecurity(...) so any database created via POST /api/v1/server {"command":"create database X"} had its entire record-level authorization system silently disabled. In combination, record-level and database-level authorization could be bypassed by any authenticated principal. This vulnerability is fixed in 26.4.2.