Ze’ev Avni ...
This article, dated 28 October 2016, says:
At the time, the Russians noted another success when they recruited a Foreign Ministry official, the economist Ze'ev Avni (born Wolf Goldstein). Avni was caught, interrogated, confessed and prosecuted under the cover of great secrecy.
It is only now, with the revelations from the Mitrokhin documents, that the full scope and sensitive nature of the information Avni passed on and the damage he caused can be truly assessed.
Avni, codenamed "Check," may have been employed by the Foreign Ministry, but starting in 1952 he was sent by the Mossad to Brussels, Belgrade and Athens. The KGB documents describe him as a "commercial attaché in Israel's Embassy in Belgrade and an operative of the Israeli intelligence in Greece and Western Germany."
The operations Avni carried out for the Mossad provided him with information on the intelligence agency's activities in Europe. According to the Mitrokhin documents, between 1955 and 1956, Avni provided the head of the KGB branch in Belgrade with the radio codes (OTPs, in intelligence jargon, meaning "one-time pad" or key) of Israeli communications. In addition, he passed on a lot of information about Mossad operatives and agents in Europe.