XTB, one of Europe's largest publicly listed brokers (WSE: XTB), experienced a major platform failure yesterday (Wednesday) that prevented clients from closing positions for several hours, leaving traders exposed to market movements without the ability to manage their risk.

However, the company’s shares at today's (Thursday’s) open did not show a sharp negative reaction to the recent run of problems, falling 0.7% and testing 70.92 zlotys.

On Thursday afternoon, XTB issued an official statement explaining the cause of the outage. Its full content is available at the bottom of the article.

XTB Platform Outage Blocks Position Closures During Trading Hours

The problems started around 4 p.m. local time when users began reporting they could open new positions but couldn't close existing ones.

“Yesterday, I wanted to show my brother how the XTB app works and how to navigate it - so we picked a random U.S. stock from the HOT category,” one retail trader from Poland told FinanceMagnates.com. “I bought around nine shares for 41 zlotys (as the minimum was 10 dollars) and from that moment the system showed an error. I have the shares in my account, but I cannot do anything with them. We then watched the position move from minus 5% to plus 21% and back down to plus 2% without any ability to manage it."

The issue persisted through the evening, with XTB announcing at 10 p.m. that all CFD trading would be suspended between 10 p.m. and 11 p.m. while engineers attempted repairs.

"We are informing you that due to problems in the functioning of our investment platform and in order to repair the technical fault, trading on CFD instruments between 22-23 will be impossible," the company said in a statement on its website. "We will keep you informed about the progress of this work on an ongoing basis. We apologize for the inconvenience."

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After the scheduled maintenance window, users could again open positions but still couldn't close them, extending the lockout well past midnight.

The problems come shortly after XTB reported a sharp decline in net profit for the third quarter - one of its weakest results since late 2022.

No Clear Timeline for Resolution

By late Wednesday evening, XTB had not explained what caused the failure or when normal operations would resume. The company's silence left traders guessing about the technical root cause and their potential losses from being unable to react to market swings.

Social media filled with speculation about the source of the problem. One theory gaining traction among technical observers suggested the platform hit a programming limit known as integer overflow, where a counter tracking transaction IDs exceeded the maximum value a standard 32-bit integer can hold.

A user posting on X under the handle kwit_flip wrote that XTB "just rolled over its INT," referring to the 4-byte integer data type. "That's why you can't close positions right now," the user claimed, noting that transaction numbers had wrapped from positive to negative values after hitting roughly 2.1 billion.

XTB właśnie przekręciło INT'a.

To jest rozmiar 4-bajtowego INTEGERA - to typ danych, którym zapisywane są transakcje na platformie @xtb. Dziś został przekroczony dodatni maksymalny numer transakcji i mamy ujemne wartości.

Dlatego nie da się w tej chwili zamknąć pozycji. pic.twitter.com/MPL4Tvj5Oe

— kwitflip (@kwit_flip) November 5, 2025

The theory remained unverified by the company.

Recent Track Record Under Scrutiny

The outage marks the latest in a series of technical problems at XTB. In a recent interview with Parkiet, board member Filip Kaczmarzyk acknowledged past platform issues while defending the company's progress.

"Of course there were moments when the platform did not work as it should, and such situations have no right to happen," Kaczmarzyk said. "It is a problem for all of us, not just for clients. However, it is definitely not the case that we only look at the platform when something bad happens. Compared to what it was two or three years ago, we have also made really huge progress."

The timing proved particularly awkward for XTB, which just days earlier announced a record 100,000 new clients in October. The company now faces questions about whether its infrastructure can handle its rapidly growing user base.

Data from Downdetector showed a sharp spike in problem reports between 4 p.m. and midnight Wednesday, then dropping to near zero afterward. On Thursday morning, however, a slight upward trend is visible again:

"So you're saying you have a product you make the most money on, where client reaction time is measured in seconds and minutes because they're trading on leverage Leverage In financial trading, leverage is a loan supplied by a broker, which facilitates a trader in being able to control a relatively large amount of money with a significantly lesser initial investment. Leverage therefore allows traders to make a much greater return on investment compared to trading without any leverage. Traders seek to make a profit from movements in financial markets, such as stocks and currencies.Trading without any leverage would greatly diminish the potential rewards, so traders In financial trading, leverage is a loan supplied by a broker, which facilitates a trader in being able to control a relatively large amount of money with a significantly lesser initial investment. Leverage therefore allows traders to make a much greater return on investment compared to trading without any leverage. Traders seek to make a profit from movements in financial markets, such as stocks and currencies.Trading without any leverage would greatly diminish the potential rewards, so traders Read this Term, but at the same time your product doesn't work for them for two hours and they can't do anything with open positions?" wrote one X user.

XTB has not yet addressed whether it will compensate clients who suffered losses during the outage or clarified the complaints process mentioned by customer service representatives.

Another Issue Following the August Hack

Given that XTB refunded client losses in August after the alleged 150,000 zloty hack drew wide attention, some investors may hope that the latest case will lead to a similar outcome.

The announcement came amid renewed pressure after the latest victim’s account gained traction on local financial forums and media outlets. The client described how hackers allegedly carried out simultaneous buy and sell orders on thinly traded securities, leaving his account consistently in loss while a separate account captured the gains. The incident has again raised questions about the platform’s security and investor protection standards.

XTB Official Statement

On Wednesday, November 5th, a technical issue occurred on the XTB trading platform, temporarily preventing clients from modifying or closing CFD positions opened after 4:25 p.m. We would like to emphasize that clients retained full access to manage positions opened earlier.

Our technology team immediately began diagnosing the situation. Implementing the necessary fixes required a temporary suspension of CFD trading between 10:00 p.m. and 11:00 p.m. At 10:40 p.m., the ability to modify new positions on the web platform was restored. By approximately 1:00 a.m. on November 6th, the same functionality was reinstated in the mobile app, fully resolving the issue.

Yesterday’s incident affected only positions opened after 4:25 p.m. - around 0.4% of a total of 25 million positions. The trades themselves were correctly recorded in the system databases; however, an error occurred when attempting to modify or close them.

The problem was caused by a technological limitation in the system responsible for transferring data between the trading engine and both the mobile and web platforms. Most of XTB’s architecture has already been rebuilt using modern technologies where such limitations have been eliminated at the design stage. The migration of position management to the new architecture is currently underway and is scheduled for completion in the first quarter of next year.

We kindly ask all investors affected by yesterday’s issue to submit complaints via the form available in the Client Office. Each case will be reviewed individually based on data from XTB’s trading system. Full details of the complaint process can albo be found on our website: https://www.xtb.com/pl/edukacja/proces-reklamacji.

The article was updated at 15:00 CET to include the statement from XTB.