XRPL sponsored-reserves fix locks sponsors in until reserves are covered
Serguey Asael Shinder2 min readThe XRP Ledger project has published a disclosure report, dated 21 September, on a vulnerability in XLS-68, the Sponsored Fees and Reserves amendment, which lets one account pay another's network fees and reserves so that end users can transact without holding XRP. The flaw was found during Devnet testing and reported on 7 August by Kris Dangerfield and Andrew Spencer, with reproduction scripts. It affected xrpld 3.3.0, but the amendment has not been activated on Mainnet or on any production network, and no funds were at risk.
The bug was in the sponsorship lifecycle. When a sponsor ended its sponsorship of a specific ledger object, such as a trust line or an offer, the code did not check whether the object's owner could cover the reserve. The object stayed on the ledger with nobody backing it, and the sponsor got its reserve back. Recycling the same capital, the reporters created 30 permanent unbacked objects at about 20 drops each, a cheap way to inflate the ledger with state no one pays for.
The report frames the root cause as a trilemma: either party should be able to leave a sponsorship at any time, every object's reserve should always be backed, and sponsored users should be able to hold zero XRP. All three cannot hold at once. The engineering team chose to drop the first. A sponsor can now end reserve sponsorship only if the sponsee funds the reserve itself, another sponsor takes over the obligation, or the object or account is deleted. As a consequence, a sponsor cannot end account-level sponsorship while the sponsee holds a dust balance below the base reserve. The team says it checked the change with pilot customers and notes the same constraint in Stellar's sponsored-reserves design.
What it means
The fix trades convenience for the ledger's accounting invariant, and it does so before activation, which is the cheapest time. For institutions that planned to sponsor users, the practical change is that sponsorship becomes a commitment that can only be handed over or closed out, not simply walked away from.