TEL AVIV — TikTok, the smartphone app beloved by teenagers and used by hundreds of millions of people around the world, had serious vulnerabilities that would have allowed hackers to manipulate user data and reveal personal information, according to research published Wednesday by Check Point, a cybersecurity company in Israel.

The weaknesses would have allowed attackers to send TikTok users messages that carried malicious links. Once users clicked on the links, attackers would have been able to take control of their accounts, including uploading videos or gaining access to private videos. A separate flaw allowed Check Point researchers to retrieve personal information from TikTok user accounts through the company’s website.

“The vulnerabilities we found were all core to TikTok’s systems,” said Oded Vanunu, Check Point’s head of product vulnerability research.

TikTok learned about the conclusions of Check Point’s research on Nov. 20 and said it had fixed all of the vulnerabilities by Dec. 15.