Following the Q2 Spring Quarterly Release, we identified that that two new permissions had been enabled by default for all API users. Any role that had "Access API" checked in the permissions for the role had "Read-Only Named Account List" and "Read-Write Named Account List" added to their permissions.
With the upcoming minor release, we will be reverting the defaults for these permissions back to disabled. After the rollback, some customers may receive an API error 603 when making API calls. Customers who receive these errors can resolve them by re-enabling the new permissions.
To manage role permissions, go to Admin > Users & Roles > Roles. Re-Enable (check) and save the two permissions shown below:
If you continue to receive 603 errors after enabling these permissions, please contact Marketo Support for further assistance.