[Bitcoin Savings App Bitstack Secures $15 Million in Series A Funding, Led by 13books Capital] BlockBeats News, December 2: French Bitcoin savings app Bitstack announced the completion of a $15 million Series A funding round, led by 13books Capital, with participation from existing investors such as YC, Serena, and Plug and Play. The new funds will be used for European expansion and product upgrades, including the launch of a VISA debit card with Bitcoin cashback (Stackback) in January 2026. Bitstack stated its goal is to become 'Europe's leading Bitcoin savings platform.'