The Wikipedia article is awful, and its entirely uncritical of the very disingenuous criticisms that Endicott and Hagerman make, which at best are ignorant of details, if not purposefully avoid engaging in good faith. The documents are much more substantiated than their phrasing would indicate, and more importantly, the narrative that the documents paint is perfectly consistent with numerous other independent datapoints which have to be completely ignored to make their own contentions have any chance of holding water. I've written on this topic before, so will repost it here:

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Claims of biological and chemical warfare being committed by the US in Korea do rear up occasionally, and stem from several accusations leveled during the conflict by the USSR, China, and North Korea. At various points this included small pox, plague, cholera, anthrax, meningitis, and encephalitis, to name some of the materials alleged at various points, with the allegations tied into US spoils from the Japanese bioweapons program during WWII.

These weren’t minor either. The claims included thousands of aerial attacks over several months in North Korea and China. One such report, from Tianjin, reads as follows:

June 9, 1952. Insects were first discovered at 12 noon near the pier at the Tanggu Workers Union Hall. At 12:40 p.m., insects were discovered at the New Harbor Works Department, and at 1:30, in Beitang town. Insects were spread over an area of 2,002,400 square meters in New Harbor, and for over twenty Chinese miles [approximately ten kilometers] along the shore at Beitang. Insect elimination was carried out under the direction of the Tianjin Municipal Disinfection Team [xiaodu dui, literally, Poison Eradication Team]. Masses organized to assist in catching insects included 1,586 townspeople, 300 soldiers, and 3,150 workers. Individual insects were collected and then burned, boiled, or buried. Insect species included inchworms, snout moths, wasps, aphids, butterflies ... giant mosquitoes, etc. Samples of the insects were sent to the Central Laboratory in Beijing, where they were found to be infected with typhoid bacilli, dysentery bacilli, and paratyphoid.

The accusations were carried to the highest levels, thrown about in the United Nations, where the US of course denied them. International representatives were brought in to produce reports, which on the face supported the allegations, but were based almost entirely on testimony, having done essentially no field study or actual investigation of the area for evidence of the supposed biological material. Almost none, in fact, spoke Chinese or had any familiarity with the country, and the commissioners evidenced an incredible amount of credulity in admitting how staged much of what they were presented looked yet not drawing much doubt. As a Swedish commissioner noted, “We accepted the word of the Chinese scientists.”

In the end, this meant that nothing concrete was ever proven, and belief or dismissal over the next few decades likely said more about ones predisposition than anything else, as there was never any real solid proof of the accusations, but plenty of people were of course happy to ignore the American denials. In the Eastern Bloc press, it was an occasional refrain for decades as a reminder of Western perfidy - and of course remains the official stance of North Korea and China to my awareness. Some notable works accepted the allegations in the interim, some simply left the issue as “open”, and others rejected them for various reasons. A not untypical description of the “did they or didn’t they” reads like this piece from John Gittings in 1975:

The fact is that there is no a priori reason why the United States should not have contemplated, or actually used, germ weapons in Korea. There may be practical reasons of a technical nature why their use might be militarily counter-productive though this has not been seriously argued. After all chemical weapons are only slightly more easy to control than bacteriological weapons; both suffer from the military disadvantage that the "contaminated" area may spread to involve one's own troops. Nor - as I have demonstrated above - can American use of germ warfare be ruled out, by those who have used the argument in the past, on the grounds that the US would have been restrained by humanitarian considerations. Both sorts of weapons have been "morally outlawed" by the world community; both are anti-personnel devices which do not discriminate between military and civilian targets.

For all but the most fervent believers though, the matter finally closed in the late 1990s, when documents from the Soviet archives surfaced which provided fairly clear evidence that the accusations were knowingly made on false information as part of a smear campaign, initially published in a Japanese newspaper after being obtained by a journalist. Memos passed between the North Koreans, Chinese, and Soviets in 1952 and '53 - principally sent to Beria - make clear reference to falsifying evidence, including preparing false areas of exposure in advance of the Commissions arrival, and then, to ensure they wouldn’t discover the ruse:

The Koreans stated that the Americans had supposedly repeatedly exposed several areas of their country to plague and cholera. To prove these facts, the North Koreans, with the assistance of our advisers, created false areas of exposure. In June-July 1952, a delegation of specialists in bacteriology from the World Peace Council arrived in North Korea. Two false areas of exposure were prepared. In connection with this, the Koreans insisted on obtaining cholera bacteria from corpses, which they would get from China. During the period of the work of the delegation, which included academician N. Zhukov, who was an agent of the MGB, an unworkable situation was created for them, with the help of our advisers, in order to frighten them and force them to leave. In this connection, under the leadership of Lt. Petrov, adviser to the Engineering Department of the KPA, explosions were set off near the place where the delegation was staying and while they were in Pyongyang false air raise alarms were sounded.

Other documents detail the assistance of Soviet advisors in helping North Korean medical personnel write up the allegations, and even details proposals by the North Korean MVD proposing to use prisoners slated for execution as stand-ins, purposefully infecting them with plague to have the necessary dead bodies for the ruse.

It also makes clear that many involved in pressing the claims likely were in the dark about the entire process, with one memo noting only in Spring of 1953 that Foreign Minister Vyshinsky might have been informed by the Soviet Embassy in North Korea that the bioweapon allegations were false, and, relatedly suggesting that the USSR should now back away from such claims. Further memos to the Chinese accuse Mao of ‘misleading’ the USSR in no uncertain terms:

For Mao Zedong: The Soviet Government and the Central Committee of the CPSU were misled. The spread in the press of information about the use by the Americans of bacteriological weapons in Korea was based on false information. The accusations again the Americans were fictitious.

A later memo in turn saw Mao passing the blame down to military commanders in Korea.

While the exact genesis of organization and execution remains murky, the evidence is clear enough that North Korea and China concocted the evidence for the accusations, with at the very least the assistance and awarenesses by the Soviet Union. And given the limited extent of the memos, which only offer part of the picture, Soviet involvement may very well have been deeper and their later protests merely putting on a show to avoid potential fallout, as some commentators note that they find it unbelievable North Korea or China would have acted without explicit authorization from Stalin at that point in time.

This still hasn’t entirely stopped the accusations. In 1999, a year after the publication of the memos, North Korea reiterated their accusations against the United States at the United Nations, and books have continued to be published which assert the truth of the matter, although generally just repeating the same old canards and innuendos without engaging with any of the real counter-evidence.
While it is true that the documents were not published by the archives themselves, and instead were copies provided to a Japanese newspaper, this is often used in an effort to try and cast far more doubt on them than is warranted. Rather than some spurious piece of questionable material smuggled out of questionable origin, the source is quite well established, with the documents provided by a Russian researcher who had access to the Soviet Presidential Archive, where the documents originated from, and the existence of the documents was confirmed by multiple former Soviet officials living in Moscow, even if not by the government itself at that time, although the Russian government never denied their veracity. Topic experts of course also provided rigorous analysis, summed up ably by Kathryn Weatherby:

Their style and form do not raise suspicion. The specifics of persons, dates and events are consistent with evidence available from a wide array of other sources. As is apparent from the translations below, their contents are so complex and interwoven that it would have been extremely difficult to forge them. In short, the sources are credible.

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