Submitted by cmichel, also found by csanuragjain and gzeon
Its possible to repeatedly add the first collateral token in validCollateral through the Whitelist.addCollateral function.
The validCollateral[0] != _collateral check will return false and skip further checks.
Owner calls addCollateral(collateral=validCollateral[0]):
The collateral parameters collateralParams are re-initialized which can break the existing accounting.
The collateral token also exists multiple times in validCollateral.
Fix the check. It should be something like:
