Putting it short, these transactions are not actually pending, they are outright invalid bundles with a signature that does not match to either the bundle or the address (or both). Your funds are still safe.
Everybody who knows your address (and has the tools) can forge such bundles and send them to a IOTA node.
But why are they shown as "Pending" on thetangle.org?
Thetangle.org is a community project, and it shows all transactions that have not been confirmed as "Pending" (including invalid transactions, conflicting transactions and incomplete bundles). While multiple people (including me) have notified the author that showing "unconfirmed" transactions as "pending" is confusing, nothing has changed so far (neither by changing the wording, nor by actually adding checks for invalid, conflicting or incomplete transactions).
And why are they transported by the network at all?
Due to design principles of IOTA (or "the tangle"), unlike other cryptocurrency protocols, a "transaction" does not describe the whole transfer of funds, but only an input or an output of it. Therefore, multiple transactions are bundled (to a "bundle") which is then signed. The signature is then split up to the transactions again. However, POW and approvals happen on transaction level (even with incomplete bundles), therefore these transactions need to be transported by the network before the bundle is complete (and the signature can be verified). So they reach tangle explorers like thetangle.org, and they decide to show them (as "pending").