Consider this: I have a repository on, for example, GitHub, and add a file I wrote.
I forget to mention the file in the license, and publish the updated version to the repository, realizing the mistake after it is too late.
So I fix the license and publish it shortly after.
Now, the old version of the repository is of course still visible, with a file not covered by any license.
Can this be exploited? If so, what can I do to protect the repository?