Hong Kong (CNN) One of the most secretive events on the Chinese political calendar ended this week with a communique that acknowledged "increasing challenges" but provided few clues as to how Beijing will address them.

It also came with a stark message for Hong Kong

The four-day plenum, which ended Thursday, came at a time of huge pressure on Chinese President X Jinping's government, including an ongoing trade war with the United States, a slowing domestic economy and violent protests in the former British colony.

The official communique only contained broad references to "increasing challenges at home and abroad." No definite plans or new policies were presented by the lengthy document.

One thing that was made clear though was that Xi is still firmly in charge, despite the recent troubles.

"The plenary session calls for the entire party and peoples of all nationalities to unite more closely around the Party Central Committee with comrade Xi Jinping as the core," the statement said.

The Communist Party Central Committee's almost 400 members meet semi-annually to formulate new policy and approve personnel changes at the top level of government. The committee met for its fourth plenum in Beijing this week.

Among praise for the government and Communist Party buzzwords, there was an ominous message from the Chinese government for Hong Kong protesters, now in their 21st week of demonstrations.

"We must establish and improve the legal system and enforcement mechanism for safeguarding national security in (Hong Kong and Macao)," the official statement read.

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Safeguarding national security

Hong Kong has now been a thorn in the Chinese government's side for more than four months.

Mass protests which began over a controversial China extradition law have grown into more violent demonstrations over fears around Beijing's tightening grip on the important financial hub.

Until now, the Chinese government has been relatively restrained on the protests, stating their support for the Hong Kong government and their faith in local authorities to resolve the crisis.

But there have been hints of tougher action by Beijing if the demonstrations grew out of control or if they crossed any of the Communist Party's "bottom lines."

"Don't ever misjudge the situation and mistake our restraint for weakness," Yang Guang, spokesman for mainland China's Hong Kong and Macao Affairs Office, said in August.

It is almost certain that the situation in Hong Kong was widely discussed behind closed doors in Beijing during the fourth plenum this week but very little of that appears in the final communique.

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"Hong Kong and Macao must be governed in strict accordance with the Constitution and the Basic Law, and the long-term prosperity and stability of Hong Kong and Macao should be safeguarded," the statement said.

It then stated the need to "improve" the legal system and enforcement mechanism in Hong Kong and Macao.

That is likely to be a euphemism for enacting Hong Kong's hugely controversial Article 23 national security law, according to Willy Lam, an adjunct professor at the Chinese University of Hong Kong and longtime analyst of Chinese politics.

"Of course we don't have hard and fast evidence but I think a logical conclusion would be the introduction of Article 23," Lam said, adding that Chinese officials had been pushing for it behind closed doors for some time.

Part of the Basic Law, Hong Kong's de facto constitution, Article 23 calls on the local government to "enact laws on its own to prohibit any act of treason, secession, sedition, subversion against the Central People's Government."

But attempts to bring it into force in 2003 led to massive protests and it hasn't been touched since.

"It would be very divisive, especially after what happened in the past four or five months," Lam said. "If Beijing were to introduce Article 23, then the stormy weather will be back. It will exacerbate conditions."

Xi triumphant

The Communist Party's plenum meetings are one of the country's main forums for major changes of party policy and have previously changed the course of Chinese history.

In 1978, it was during a plenum that then-Paramount Leader Deng Xiaoping began the policy of economic opening which would turn China into an economic powerhouse.

It was at the second plenum in January 2018 that the Communist Party agreed to remove term limits on the office of the Chinese presidency, effectively allowing Xi to remain president for life.

In the lead-up to this week's plenum, there were rumors of possible personnel changes at the top levels of the Chinese government which could begin to outline a successor to Xi.

The Party Secretary of industrial city Chongqing, Chen Min'er, was reported to be in the running for a seat on the Communist Party's Standing Committee. It would have been a huge promotion and a clear sign of big things to come.

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It followed whispers of dissatisfaction with Xi and his tight grip on power. Since the trade war with the US began in mid-2018, it had been rumored that opposition to the Chinese president was growing behind closed doors. So far, Xi has even refused to nominate any potential successor, a break from modern Communist Party tradition and a sign that he retains a significant hold on power.

In the end, there were no major changes, and no personnel announcements other than the automatic promotion of two new alternate members to the Central Committee.

Instead the president and his signature Xi Jinping Thought are mentioned prominently in the communique, from domestic and international policy to military advancement.

"We must firmly establish the guiding position of Xi Jinping's strong military thinking in national defense and army building," the statement says.

If the communique is an accurate representation of what happened behind closed doors, Xi Jinping is here to stay.