Geneva: Currently a fellowship of about 340 churches, of which 157 are official members. Its membership includes most of the Orthodox Churches and numerous Protestant Churches. The Eastern Churches would seem to have hegemony within the organization.
The group stresses ecumenicism; however, this apparently translates to the usage of the term meaning attempted ecumenicism across Christian denominations. The Roman Catholic Church sends observers to official meetings, but is not a member. Politically, the WCC over the decades has typically and fairly consistently been more pro-Arab and anti-Israel than the Vatican.
The WCC is not, shall we say, on the Top Ten List of friends of Judaism and the Jews. It would officially profess rejection of anti-Semitism, but many of its constituent Churches make the Vatican look good in that regards.
One can make the case that anti-Semitism embedded within the informal ideology of some of the constituent Orthodox Churches, finds its expression in the consistently (and often strident) anti-Israel official postures of the WCC.
This potential phenomenon, just-noted, is hard to distinguish from political anti-Semitism, an often virulently anti-Israel quasi-theology which has vexed, if not traumatized, Jewish students at college campuses around the world, including Jewish-American students at many dozens of campuses across North America and beyond.
In the parallel universe occupied by political anti-Semitism, Arab terror is ignored or justified; Israeli counter-measures are painted as genocidal.