In December 1993 he was severely injured when he opened a letter bomb which had been sent to his home in Innere Stadt by Franz Fuchs.

[1] In October 1998, the newspaper Süddeutsche Zeitung accused Helmut Zilk of having collaborated with Czechoslovak secret police (StB) during the 1960s.

Zilk had provided information about the political situation in Austria and assessments of individual Austrian politicians; for this he was paid in money and goods such as Bohemian crystal glass.

[3] After the Soviet occupation of Czechoslovakia (August 1968) Ladislav Bittman, one of the agents in contact with Zilk, defected to the West and leaked information about him.

Some Czech media (as well as the old StB documents) speculated that the continued political and journalistic career of Zilk, in spite of being uncovered, was due to some other agency (CIA is suggested) recruiting and supporting him.