paymentrequest.py in Electrum before 4.2.2 allows a file:// URL in the r parameter of a payment request (e.g., within QR code data). On Windows, this can lead to capture of credentials over SMB. On Linux and UNIX, it can lead to a denial of service by specifying the /dev/zero filename.

Electrum Technologies GmbH Electrum Bitcoin Wallet version prior to version 3.0.5 contains a Missing Authorization vulnerability in JSONRPC interface that can result in Bitcoin theft, if the user's wallet is not password protected. This attack appear to be exploitable via The victim must visit a web page with specially crafted javascript. This vulnerability appears to have been fixed in 3.0.5.