Evidence

Multiple independent Ukrainian and international outlets — Kyiv Independent, Ukrainska Pravda, Mezha, and Yahoo News (citing wire coverage) — report that Mykhailo Puryshev, a prominent Ukrainian volunteer, publicly stated in mid-August that Russia's FSB had blackmailed him over his 18-year-old son, who lives in Russia and was allegedly threatened with conscription into the Russian army. According to these reports, Puryshev said he travelled to Moscow to try to save his son, and days later released a video statement confirming he was safe and had returned to Ukraine. The claim originates directly from Puryshev's own public statements (via social media/Instagram and interviews, e.g. with hromadske.ua), which were then reported by these outlets, rather than being independently verified through forensic or intelligence-based confirmation of FSB involvement. I found no dedicated fact-check from Reuters, AFP, Bellingcat, or EUvsDisinfo specifically assessing the truthfulness of the blackmail claim itself.