Over the past several months the price of STEEM has dropped dramatically and that has introduced some issues for SBD, which is a stable value coin (aka stablecoin) backed by about $1 worth of STEEM. As part of the implementation of SBD, there is a rule which gradually reduces the backing of SBD below $1 when STEEM's value becomes too small to support all of the SBD in circulation at the full $1 value (in addition there are mechanisms to reduce the amount of SBD, but that is not relevant to this post). The way this is done is by adjusting the price feed provided by witnesses so that the system assumes STEEM is worth a bit more than it is when performing internal calculations.
The price feed adjustment is normally reasonably small and, while this would introduce an inaccuracy in values on UIs (including steemit.com) which rely on the price feed for their estimate of the price of STEEM (such as steemit.com), the inaccuracy would be quite small (similar to other such inaccuracies in displayed values due to factors such as changing market prices, changes in the size of the reward pools, etc.). However, due to a bug in the popular steem-js library, steemit.com and another of other UIs (including steempeak and steemworld) have experienced a dramatic inaccuracy as well as various other malfunctions (such as post payout detail being incorrect). I reported this bug several hours ago upon identifying it, but it has not yet been fixed. EDIT: @eonwarped also found and fixed some additional issues in condenser itself.
Some of the other UIs have introduced their own work-arounds for the problem but currently steemit.com is not yet fixed.
After some quick investigation in cooperation with @timcliff, as far as I know the problem occurs only in the UI (display) layer and does not affect any blockchain calculations.
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