Martin Luther King was mentioned in history textbooks in the Soviet bloc as an influential figure who was assassinated by the US government as evidence of race-based class repression in America but since he was not a socialist/communist activist and was a religious minister he wasn't made prominent and was mentioned in passing. It was more about the evidence that America was a typical capitalist society as defined by Marx rather than explaining in detail the nature of the CRM. It was also regularly linked with the ongoing wars in Indochina/Vietnam as an example of America engaging in an attempt to maintain a colonialist/imperialist political system worldwide - both in their own country and abroad. Since America also took over the mantle of the power from France and Britain it was also presented a "capitalism" fighting against "forces of freedom and progress".

Malcolm X was mostly forgotten since he was considered less relevant politically and his legacy - which is actually quite damaging to the CRM - could not be unanimously presented as "armed fight for political justice" or some similar thing. Some textbooks mentioned him as a victim of assassination, some textbooks didn't.

In other words it was mentioned but at the same time completely subsumed into the dogma of Marxian historical narrative.

The academic textbooks would have more information on both leaders but that would be university-level history and it was more closely scrutinized on the personal level by the security services, since it was considered that King could be used as an example of successful civil resistance against communist authorities, especially considering his religious background.

In general you have to remember that King or Malcolm X are a big thing in America and are rarely bothered with to any greater extent in Europe. The same goes to the attitudes Europeans and especially former Soviet-bloc Europeans have towards slavery/racism/etc. In Western Europe it is mostly their own colonial past and nation-based imperialism while in Eastern Europe it's a "what?".

Also your question is incorrectly formed. The main distinctions between peoples in the Soviet bloc were between the Soviet Union (communist since 1922 and ruled by communists domestically) and the Soviet bloc (communist since circa 1948-49 as a result of Soviet occupation). There would be differences between what people in the USSR and the Soviet bloc countries would be told. Then there would be further differences between the several occupied countries of the bloc. East Germany in particular had a strong focus on German history and Nazi-West links and the ongoing attempt to undermine "the Republic".