He added that this gave access to records that included thousands of customers’ national identity numbers.
Last week, the firm revealed a separate attack affecting millions in the US.
After being notified of the latest breach, Equifax temporarily shut the affected website.
“We learned of a potential vulnerability in an internal portal in Argentina which was not in any way connected to the cyber-security event that occurred in the United States last week,” an Equifax spokeswoman told the BBC.
“We immediately acted to remediate the situation, which affected a limited amount of information strictly related to Equifax employees.
“We have no evidence at this time that any consumers or customers have been negatively affected, and we will continue to test and improve all security measures in the region.”
The discovery came less than a week after Equifax revealed that a separate breach meant about 143 million US consumers and an undisclosed number of British and Canadian residents might have had personal details exposed.
The firm took six weeks to make the discovery public after first learning of a problem.
On Tuesday, 36 US senators called for a federal investigation into how three company executives came to sell nearly $2m (£1.5m) worth of shares in the company in the interim.
Equifax is also facing dozens of legal claims over the matter.
Mr Krebs wrote that the Argentine matter involved Equifax’s local business Veraz.
Specifically, a web application – referred to as Ayuda, the Spanish for “help” – appears to have been weakly guarded.
“[It] was wide open, protected by perhaps the most easy-to-guess password combination ever: admin/admin,” wrote Mr Krebs.
The discovery was made by the US cyber-security firm Hold Security, which Mr Krebs advises.
Its researchers explored the portal and within found a list of more 100 Argentina-based employees, the blogger disclosed.
Using this list they were able to uncover the workers’ company usernames and passwords, which turned out to be matching words in each instance.
Each example amounted to either solely the worker’s last name or a combination of their surname and their first initial, which made them fairly easy to guess anyway, Mr Krebs added.
“But wait, it gets worse,” he blogged.
“From the main page of the Equifax.com.ar employee portal was a listing of some 715 pages worth of complaints and disputes filed by Argentinians who had at one point over the past decade contacted Equifax via fax, phone or email to dispute issues with their credit reports.
“The site also lists each person’s DNI [documento nacional de identidad]- the Argentinian equivalent of the social security number – again, in plain text.”
All told, there were more than 14,000 such records, Mr Krebs said, concluding that the firm had been “sloppy”.
One UK-based cyber-security expert agreed.
“This kind of security vulnerability is extraordinary as even the most basic of checks should reveal this,” Prof Alan Woodward from the University of Surrey told the BBC.
“It’s outrageous that any organisation that holds such sensitive personal data can build a portal with this kind of basic security vulnerability.
“It simply shouldn’t happen and responding that they have now fixed the issue is not the point: it puts a huge question mark over whether Equifax have been applying the appropriate resources to online security elsewhere.”
“Where is Santiago Maldonado?” Social media in Argentina is chiming with the same phrase, loaded with anger and frustration.
The protester, 28, went missing at an indigenous-rights demonstration in Patagonia at the start of August.
On a Saturday night talk show, the national security minister said she was sure the police were not involved.
Witnesses say Mr Maldonado was arrested and not seen again.
The police have denied detaining him.
“The police are not the same as 40 years ago,” said Security Minister Patricia Bullrich, referring to the country’s military dictatorship. Rights groups say up to 30,000 people “disappeared” when a brutal junta ruled from 1976 to 1983.
She urged people not to make the case a “political battle”, saying the government and human rights organisations were aligned in trying to find out the truth.
But Argentina’s history of political disappearances has made the case an extremely hot subject.
The government has offered a reward of almost US$30,000 (£23,000) for information on his disappearance.
The former president, now head of the opposition, Cristina Fernández de Kirchner has repeatedly spoken out on the disappearance, which also coincided with the first round of congressional elections.
“Santiago must reappear. And he must reappear alive,” she tweeted.
The mystery gripping a nation
What happened on 1 August is entirely unclear.
“It truly is an enigma,” said television host Mirtha Legrand, during her show when she grilled the security minister.
After the interview aired, Argentinians ramped up the online protests, posting Facebook status updates with their name and current location, adding, “But where is Santiago Maldonado?”
“I am Mariana. I am in my house, waking up in the morning, and I want to know, where is Santiago Maldonado?” read a typical example, posted on Sunday.
Ms Bullrich has previously said there is no proof that Mr Maldonado was even present at the protest, which took place in Cushamen, in Chubut province, as “all the people were hooded”.
The polarised Argentine press has been filled with rumours, from backing allegations that the police were involved to suggesting that an indigenous-rights protester of the Mapuche community killed him.
One witness account says he was seen when a group crossed a river to escape the police, who were said to be firing lead and rubber bullets.
“We saw him clinging to a tree, not crossing the river,” Mapuche protester Soraya Maicoño told news site Infobae, saying he then went out of view after they heard someone tell him he was being detained. “After that, we did not see him again.”
However, key witnesses have refused to testify in court, which the authorities say is hampering investigations.
The Mapuche’s protest
The Cushamen protest was held to defy the detention of Mapuche leader Facundo Jones Huala, who heads the Ancestral Mapuche Resistance (RAM) separatist group.
Jones Huala is in a Chubut jail, and the Chilean government, which considers him a terrorist, has requested his extradition.
A community of Mapuche have been occupying land in the Chubut, claiming ancestral rights in a privately owned area.
On the day that Mr Maldonado disappeared, border police arrived to dismantle a protester roadblock which had been erected on Route 40, the main road that connects the country from north to south.
‘I can’t look at my son’s face on a flag’
Earlier this month, a march was held in Buenos Aires calling for Santiago Maldonado’s safe return.
Another march was held in the city of La Plata last week, but it took a violent turn when a protester threw a Molotov-type bomb at the provincial Senate building.
Mr Maldonado’s brother insists his sibling is “not a militant or an activist”, but just had empathy for the cause.
The craftsman, who was often travelling, had recently moved to the bohemian Patagonian town of El Bolsón, where he was living with others in a community library.
Now he is becoming a symbol for various conflicts, from indigenous rights to alleged government repression.
A giant mural of him has been created in his parents’ home town in Buenos Aires province.
“I can’t look at my son’s face on a flag or in a mural,” said his father, Enrique, in an interview with La Nación newspaper on Friday. “Please let him reappear. Where is he? What have they done to him?”
The family say they have agreed to give samples of blood and saliva to check with the DNA of blood and hair found in a police van.
BUENOS AIRES (Reuters) – Argentina’s main labour unions took to the streets of the capital on Tuesday demanding more jobs and protesting centre-right President Mauricio Macri’s economic policies.
Tens of thousands of workers gathered in the historic Plaza de Mayo criticizing Macri, who is trying to lower labour costs to attract investment and jump-start an economy that emerged from recession in the second half of last year.
“If some retrograde (in the government) thinks that lowering wages, precarious living conditions and destroying trade unions is going to line up investments… we say that is very wrong,” said Juan Carlos Schmid, a leader of Argentina’s largest umbrella union, the CGT.
Standing on a podium at the protest, he said the CGT would meet in late September to discuss a potential strike.
Macri told Reuters in an interview this month his government was negotiating labour agreements sector by sector rather than trying to pass a comprehensive labour reform like the one approved in neighbouring Brazil.
Unions fear more drastic changes could be coming after mid-term legislative elections in October, however, especially after a primary vote on Aug. 13 pointed to strong support for Macri’s coalition.
Macri is trying to open Argentina’s long protected economy and focus on competitive industries like oil and agriculture, but has seen some manufacturing jobs lost in the meantime.
The most recent employment data showed the jobless rate rose to 9.2 percent in the first quarter of the year from 7.6 percent in the fourth quarter of last year.
Reporting by Nicolas Misculin and Caroline Stauffer; Editing by Sandra Maler
BUENOS AIRES (Reuters) – Argentines vote on Sunday in a closely watched mid-term primary election that will test their appetite for bringing back the left-wing populism of former President Cristina Fernandez.
Fernandez, who was indicted for corruption last year, is vying for a Senate seat in Buenos Aires province, home to nearly 40 percent of the country’s voters. She is running against business friendly President Mauricio Macri’s former education minister and other candidates from a divided opposition.
Investors and wealthy Argentines fear a Fernandez comeback in Congress could pave the way to her running for president in 2019. Her return to power would likely mean the end of Macri’s reforms and a resumption of rampant spending, protection of industry and isolation from trade agreements and international capital markets.
A seat in Congress would give the 64-year-old Fernandez immunity from arrest, though not from trial. She dismisses the corruption accusations as politically motivated.
The compulsory primary vote on Sunday will essentially serve as a detailed poll ahead of the Oct. 22 election for one third of the Senate and half the lower house of Congress, as no major candidates are being challenged from within their own parties.
Though her chosen successor lost to Macri in Buenos Aires province in 2015, Fernandez now appeals to many in its struggling industrial belt, where Argentina’s emergence from recession in the second half of last year has yet to take hold.
The final weeks of primary campaigning were marked by repeated headlines highlighting gaffes from Esteban Bullrich, Macri’s former education minister and scion of a wealthy Buenos Aires family. On Wednesday he apologised for calling the jailing of young people “progress.”
Bullrich had previously suggested craft beer as an alternative employment opportunity for Argentines who had lost their jobs and was criticized by feminists for a radical anti-abortion stance.
Fernandez, who broke with Argentina’s main opposition movement of Peronism for the election as some adherents form more moderate factions, meanwhile ran a relatively subdued campaign compared to her often fiery rhetoric and long speeches as president.
“We weren’t always as humble as we should have been,” she said of her presidency at her final rally.
Argentina’s peso has weakened around 9 percent since Fernandez, who was president from 2007 to 2015, formed a new political party and declared her candidacy on June 24 even as the central bank sold $1.8 billion to curb the currency’s drop.
In an interview for the Reuters Latin America investment summit, Macri admitted the race would be tight in Buenos Aires province but insisted that, more importantly, his coalition would win on a national level.
No matter how many seats his “Let’s Change” coalition picks up, Macri will still lack a majority in Congress and continue to need to build alliances to pass reforms.
An opponent like Fernandez representing the country’s most powerful economic district could make that all the more difficult.
“Labour, retirement and tax reform will require an agreement,” said political analyst Rosendo Fraga. “If it wins Buenos Aires, the government will go into these negotiations strengthened, if it loses it will be much weaker.”
Reporting by Caroline Stauffer; Editing by Mary Milliken