Credit Suisse ($CS@Switzerland) shares fell 9.5 percent by 11:16 a.m. London time Friday morning, ending a turbulent week for the global investment bank. Shares closed at an all-time low on Wednesday before rallying 18 percent on Thursday. The bank is in the midst of a major overhaul after a string of losses and scandals. The U.S.-based CS First Boston branched off from Credit Suisse, reducing Credit Suisse’s exposure to risk-weighted assets. The Swiss bank also secured $4.2 billion in capital funded by Saudi National Bank, acquiring a 9.9 percent stake. Credit Suisse’s default risk has risen to crisis levels, with the 1-year CDS rate finishing Thursday at 34.2 percent.