IBKR does not automatically adjust existing orders after the ex-dividend date on stocks which have declared an ordinary dividend. On the other hand, IBKR will automatically cancel existing orders when the following conditions have been met:

• If a corporate action on a security results in a stock split (forward or reverse), exchange for shares, or distribution of shares.
• If you do not log into your IBKR account for 90 days.
• At the end of the calendar quarter following the current quarter. For example, an order placed during the third quarter of 2011 will be canceled at the end of the first quarter of 2012. If the last day is a non-trading day, the cancellation will occur at the close of the final trading day of that quarter. For example, if the last day of the quarter is Sunday, the orders will be cancelled on the preceding Friday.
• Orders that are modified will be assigned a new “Auto Expire” date consistent with the end of the calendar quarter following the current quarter.

Generally speaking, it is the client's responsibility to be aware of pending corporate actions and how such events will affect their outstanding orders and portfolio.