Logminer showing an update that could not have happened

Dear Oracle Experts,

User A complained about unexplained changes in one of his tables.
Since he had an exact timestamp of when the data changed, I decided to
use logminer to look into it.

I filtered the logminer results to show me just the specific segment
that changed, so I filtered by seg_name="T1" and seg_owner="A".
Then I looked at username, session#, session info, sql_redo and sql_undo.

From the information in the log miner, it looked like user B updated
the table that belongs to user A.
(i.e. username is B, login_user inside session_info was user B,
machine in session_info was user B's desktop, and SQL Redo was "update
A.T1....")

The problem is that user B does not have the required privileges to do
this update. I double checked that by logging in as user B, tried to
run the exact update I was in the logminer table and received:
ORA-01031: insufficient privileges
Just like I expected from examining sys privs, object privs and roles.

One possibility is that the privileges were changed after the update
happened. I seriously doubt it, but currently its the only theory I
have.

Is there other possibilities? Can I be misreading the log miner table?

I'll appreciate any hints and directions.

Thanks,
Chen Shapira
--
http://www.freelists.org/webpage/oracle-l

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