A DW article says
Malaysia stood out as a country that refused IMF assistance and advice. Instead of further opening its economy, Malaysia imposed capital controls, in an effort to eliminate speculative trading in its currency. While the IMF mocked this approach when adopted, the Fund later admitted that it succeeded.
It doesn't give more details though... (Based on previous paragraphs in the article, it seems to be in the context of the 1997 Asian financial crisis.) So is this true, was there an instance when the IMF made such an admission?