Writing SQL injection proof dynamic DDL in Oracle I have a need to write dynamic DDL statements such as CREATE USER ?. I know that I can use EXECUTE IMMEDIATE to do this, but so far I have found no way to incorporate dynamic parameters without simply concatenating strings, which leaves me open to SQL injection.

Coming from PostgreSQL I an used to being able to quote identifiers or using FORMAT to safely put identifiers into a formatted string that can then be executed. Is there anything like this in Oracle (particularly 12c)? If not, how does one perform such dynamic SQL safely?
DBMS_ASSERT might be what you're looking for:

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║         Subprogram          ║                                           Description                                            ║
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║ ENQUOTE_LITERAL Function    ║ Enquotes a string literal                                                                        ║
║ ENQUOTE_NAME Function       ║ Encloses a name in double quotes                                                                 ║
║ NOOP Functions              ║ Returns the value without any checking                                                           ║
║ QUALIFIED_SQL_NAME Function ║ Verifies that the input string is a qualified SQL name                                           ║
║ SCHEMA_NAME Function        ║ Verifies that the input string is an existing schema name                                        ║
║ SIMPLE_SQL_NAME Function    ║ Verifies that the input string is a simple SQL name                                              ║
║ SQL_OBJECT_NAME Function    ║ Verifies that the input parameter string is a qualified SQL identifier of an existing SQL object ║
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That same page also links to some examples on how you can avoid SQL injection.