According to CoinMeta, the Electrum wallet fixed a high-risk vulnerability this weekend. This vulnerability allowed malicious servers to manipulate pending Bitcoin transactions and redirect funds to addresses controlled by attackers. The vulnerability affected all versions prior to 4.8.3, and a fix has now been released. At least some users have confirmed that they lost funds due to this vulnerability. The attack took advantage of the wallet's trust model for unconfirmed transactions; attackers could interfere with users' actual transactions by forging them. Electrum Developer Sombernight pointed out that attackers could deceive users by matching the output address of the forged transactions with the last four characters of the user's intended address. The fix for this vulnerability was marked in the code repository on October 23rd, and the binary file was released the following day. Users who are unable to update their wallets immediately should manually verify the output address and amount.