stm32f103 says it is normaly configured as pull up but im not convinced that is the case. #39
Description
The documentation tells us this:
/// This constructor sets the pin direction to input.
/// By default, the internal weak pull-up is enabled.
The mode cnf wil be set to 1000.
But as can be seen in above image this depends on the PxODR register. So if it was an output before and it was put low it will be a pull down.