Does green tea extract supplement cause liver damage?

It has been reported. "Pharmaceutically analysis (HPLC) of the green tea capsules did not give evidence for contaminants but revealed the two typical compounds of green tea, namely (-)-epigallocatechin-3-O-gallate (EGCG, 93.2%) and epicatechin (EC, 6.8%) at a very high dose level." https://pubmed.ncbi.nlm.nih.gov/24862489/

Even though not known as a major hepatotoxic supplement, cases of liver failure have been described. If any suspicion, stop taking the supplement and let your doc know.