The Soviet space program started a manned initiative in the December 1976 out of the existing Interkosmos program (sometimes anglicanized Intercosmos) which was venue for the Warsaw Pact and other Soviet-friendly nations to explore space. The main vehicle for this venture was the Soviet space program's response to the Apollo successes, the Salyut space stations. Wikipedia has a good list of the manned Interkosmos missions.

The Interkosmos program operated along the lines of prior Soviet space initiatives, namely a curious mixture of public propaganda and obsessive secrecy. In a 2011 Der Spiegel interview with the GDR cosmonaut Sigmund Jähn, he maintains that he did not know he was selected for spaceflight training until he arrived at Star City in the USSR. Nevertheless, candidates were screened for political reliability and usually came from the air forces of the various nations. Although given titles like Mission Specialist or Flight Engineer, the Interkosmos personnel were usually subordinate to a Soviet cosmonaut, leading to some jokes about the need for Soviet minders in the Warsaw Pact. But the Interkosmos flights were highly publicized and often laden with symbolic importance. The Czechoslovakian Vladimír Remek's flight occurred ten years after the events of Prague Spring and was supposed to symbolize the healed rift between the Czechoslovakians and the Soviets. Soyuz 37's flight coincided with the Moscow Olympics and had the Vietnamese VPAF aviator Phạm Tuân who was a national hero for allegedly shooting down a B-52 in Operation Linebacker II. Tuân's mission was to do an environmental survey of Vietnam from space and not surprisingly, his report concluded that US military action had severely damaged the Vietnamese environment.

But beyond Interkosmos, the Warsaw Pact states were involved in space by producing hardware for the Soviet space program, both for military and scientific purposes. The GDR firm Zeiss produced a number of cameras and other sensors that went up on Soviet rockets. GDR semiconductors also found their way in orbit by the 1980s as the GDR was one of the centers for the production of microchips in the Warsaw Pact. Warsaw Pact engineers and specialists sometimes assisted the Soviet program in data analysis.

Sources

Augustine, Dolores L. Red Prometheus: Engineering and Dictatorship in East Germany, 1945-1990. Cambridge: MIT Press, 2007.

Sheehan, Michael. The International Politics of Space. London: Routledge, 2007.