Functions without a visibility type specifier are public by default in solc < 0.5.0.
This can lead to a vulnerability where a malicious user may make unauthorized state changes.
solc >= 0.5.0 requires explicit function visibility specifiers. (see here)
- Function: public/external/internal/private
- solc < 0.6.0
- Default: Public
- Unauthorized Access Removed ->
solc 0.5.0 - Explicit Function Visibility