On Monday (17 September 2018)  a vulnerability (known as CVE-2018-17144) in Bitcoin Core (Bitcoin's reference implementation)  which had existed since version 0140 of Bitcoin Core (released on 8 March 2017)  was reported to developers working on Bitcoin Core as well as some projects supporting other cryptocurrencies that use this code (such as "Bitcoin ABC" and "Bitcoin Unlimited"  the two leading full node implementations of the Bitcoin Cash protocol)