Do not propagate taint through object.__class__

Summary: Add a model to stop propagating taint through object.__class__

Reviewed By: tianhan0

Differential Revision: D76519087

fbshipit-source-id: 4c3371a960a2ff0b21a35370f3b7de43dc1f40ef

Author: arthaud

stubs/taint/common/builtin_functions.pysa

@@ -36,3 +36,9 @@ def filter.__new__(cls, function, iterable: TaintInTaintOut[LocalReturn, Paramet
 # `next()` with a single argument is hardcoded in the analysis.
 @SkipObscure
 def next(__i: TaintInTaintOut[Collapse], __default: TaintInTaintOut[LocalReturn, NoCollapse]): ...
+
+# Don't propagate taint through .__class__
+@SkipObscure
+@Sanitize
+@property
+def object.__class__(): ...