Microsoft confirmed that third parties will be allowed to study and test its security patches before they are commercially released.
However, this has led to fears that unscrupulous employees could be tempted to leak details of Microsoft software vulnerabilities before patches are released.
Until last week, Microsoft had denied such a practice. But it is now allowing a select group of users to beta test security patches in an effort to minimise potential errors.
Microsoft has so far only named the US Air Force as being an organisation on its patching review list, but it is believed commercial organisations are also on it.