As disclosed by the Delta Chat Team today (link below), several security issues were fixed in the deltachat-core-rust library. The version of the library containing the fixes is incorporated in DeltaTouch 1.4.0 as released on March 6.
It's strongly advised to update to DeltaTouch version 1.4.0, if you haven't already.
Impressive work by the DC Team and ETH Zürich, check out the blog post: https://delta.chat/en/2024-03-25-crypto-analysis-securejoin