LONDON — When Julian Assange, the WikiLeaks founder, jumped bail and sought asylum in Ecuador’s embassy five years ago to avoid a Swedish rape investigation, he was considered by many a hero of transparency, internet freedom and resistance to the secret state.

So when Sweden’s prosecutors announced on Friday that they were abandoning their attempt to extradite him, invalidating the warrant for his arrest, Mr. Assange proclaimed it a happy moment of vindication. “Today was an important victory,” he said.

But Mr. Assange, 45, who became a persistent problem for the Obama administration and Hillary Clinton’s presidential campaign over leaks of classified and embarrassing documents, still faces enormous legal problems — which he also acknowledged.

He could be arrested in London for other reasons — and may possibly risk extradition to the United States — if he left the sanctuary of Ecuador’s embassy. And his reputation is far different than when he entered it in 2012.