Submitted by: @pavel-zotov

SQL> show version;
ISQL Version: WI-T3.0.0.31690 Firebird 3.0 Beta 2
Server version:
Firebird/Windows/Intel/i386 (access method), version "WI-T3.0.0.31690 Firebird 3.0 Beta 2"
Firebird/Windows/Intel/i386 (remote server), version "WI-T3.0.0.31690 Firebird 3.0 Beta 2/tcp (csprog)/P13"
Firebird/Windows/Intel/i386 (remote interface), version "WI-T3.0.0.31690 Firebird 3.0 Beta 2/tcp (csprog)/P13"
on disk structure version 12.0

SQL> with
CON> x as(
CON> select 1 i from rdb$database
CON> )
CON> ,y as(
CON> select i from x
CON> )
CON> select * from y
CON> as x -- <<<<<<<<<<<<<<<<<<< NB: `x` is also used for 1st part of this CTE, but it CAN be placed here because it is finish of all query
CON> ;
Statement failed, SQLSTATE = 42000
Dynamic SQL Error
-SQL error code = -104
-CTE 'X' has cyclic dependencies

No such error on WI-V2.5.4.26842.
There are also no errors in similar queries on MS SQL and Postgress.