Smartraveller's advice for Ukraine mentions the terrorism threat for Europe:
There is an ongoing threat of terrorism in Europe. In the past, terrorist attacks have occurred in a number of European cities.
Terrorism is a threat throughout the world. See our Terrorist Threat Worldwide bulletin.
Their page Terrorist Threat Worldwide says
We assess that a heightened risk of terrorist attack exists in a number of European countries due to the conflict in Syria and Iraq. In the past decade, major terrorist attacks have occurred in a number of European cities, such as Moscow, Oslo, Volgograd, Paris, Brussels, Nice and Berlin. Targets have included public transport and transport hubs as well as public places frequented by foreigners. European security services are taking robust measures in response to the current threat, particularly over the Christmas/New Year period. On 19 December 2016 a truck drove through a crowded evening Christmas market in Berlin, causing a number of deaths and injuries. An attack in July 2016 in Germany, involving a radicalised person attacking train commuters with an axe, underscores the ongoing risk of attacks by individuals and small groups.
I'm aware of terrorist attacks affecting Western Europe (including Scandinavia), and Turkey, and possibly Russia, but I haven't heard about recent terrorist attacks affecting Eastern Europe (apart from the Ukraine conflict, which usually wouldn't be categorised as terrorism).
Is Ukraine generally regarded as affected by a heightened risk of terrorist attack? What about nearby Eastern European countries which are part of the Schengen area?