Submitted by: @pavel-zotov

New database, on WI-T3.0.0.31840:

C:\MIX\firebird\QA\fbt-repo\tmp>C:\MIX\firebird\fb30\isql localhost/3333:e30
Database: localhost/3333:e30
SQL> create table test(id int, s varchar(10)); commit;
SQL> create or alter user c1234 password '123'; commit;
SQL> revoke all on all from c1234;
Warning: ALL on ALL is not granted to C1234.
SQL> commit;
SQL> grant select on test to c1234; commit;
SQL> grant update (id) on test to c1234; commit;
SQL> insert into test values(1, 'qwerty'); commit;
SQL> connect 'localhost/3333:e30' user 'c1234' password '123';
Database: 'localhost/3333:e30', User: c1234
SQL> show grants;

/* Grant permissions for this database */
GRANT SELECT, UPDATE (ID) ON TEST TO USER C1234 --------------- <<< ::: NB ::: user can modify only ONE column, `ID`.
SQL> select * from test;

      ID S

============ ==========
1 qwerty

SQL> update test set s='asdfgh';
SQL> commit;
SQL> select * from test;

      ID S

============ ==========
1 asdfgh

Similar actions on WI-V2.5.5.26871:

C:\MIX\firebird\QA\fbt-repo\tmp>C:\MIX\firebird\fb25\bin\isql localhost/3254:e25
Database: localhost/3254:e25
SQL> create table test(id int, s varchar(10)); commit;
SQL> drop user c1234; commit;
SQL> create user c1234 password '123'; commit;
SQL> revoke all on all from c1234;
Warning: ALL on ALL is not granted to C1234.
SQL> commit;
SQL> grant select on test to c1234; commit;
SQL> grant update (id) on test to c1234; commit;
SQL> insert into test values(1, 'qwerty'); commit;
SQL> connect 'localhost/3254:e25' user 'c1234' password '123';
Database: 'localhost/3254:e25', User: c1234
SQL> show grants;

/* Grant permissions for this database */
GRANT SELECT, UPDATE (ID) ON TEST TO USER C1234
SQL> select * from test;

      ID S

============ ==========
1 qwerty

SQL> update test set s='asdfgh';
Statement failed, SQLSTATE = 28000
no permission for update/write access to COLUMN TEST.S

Commits: 58bba21 FirebirdSQL/fbt-repository@b36b53c