To implement secure communications, the curl package needs to connect with a library that handles the SSL (secure socket layer) encryption. On Linux and Macs, curl has always used the OpenSSL library, which is included on those systems. Windows doesn’t have this library (at least, outside of the Subsystem for Linux), so on Windows the curl package included the OpenSSL library and associated certificate. This raises its own set of issues (see the post linked below for details), so version 3.0 of the package instead uses the built-in winSSL library. This means curl uses the same security architecture as other connected applications on Windows.
This shouldn’t have any impact on your web-connectivity from R now or in the future, except the knowledge that the underlying architecture is more secure. Nonetheless, it’s possible to switch back to OpenSSL-based encryption (and this remains the default on Windows 7, which does not include the winSSL).
Click through for more information.