Alyssum murale is an annual herb that is not native to California.
There is a high risk of this plant becoming invasive in California according to Cal-IPC.
[Cal-IPC] Europe Native, Habitat: Alyssum murale (yellowtuft) is a perennial herb (family Brassicaceae) with tiny yellow flowers and narrow leaves found in the southern and northeastern ranges of Oregon. It is native to Southeastern Europe. It favors woodland habitats. It spreads via wind and human activities. Its seeds attach to nearby growing plants. (link added by Mary Ann Machi)