Vyper 0.1.0b1 before 0.1.0b17 and 0.4.1 through 0.5.0b1 builds its source-line table with str.splitlines(), which treats characters like form feed and U+2028 as line breaks the Python parser ignores, so numeric literals are classified and validated from shifted source text. An attacker contributing source code can hide these characters in comments, strings or indentation to silently change address, integer or decimal constants.