os.OpenFile(path, os.O_CREATE|O_EXCL) behaved differently on Unix and Windows systems when the target path was a dangling symlink. On Unix systems, OpenFile with O_CREATE and O_EXCL flags never follows symlinks. On Windows, when the target path was a symlink to a nonexistent location, OpenFile would create a file in that location. OpenFile now always returns an error when the O_CREATE and O_EXCL flags are both set and the target path is a symlink.

Calling Verify with a VerifyOptions.KeyUsages that contains ExtKeyUsageAny unintentionally disabledpolicy validation. This only affected certificate chains which contain policy graphs, which are rather uncommon.

Proxy-Authorization and Proxy-Authenticate headers persisted on cross-origin redirects potentially leaking sensitive information.