7. Given that the parabola $P$ has the center of the ellipse $E$ as its focus, $P$ passes through the two foci of $E$, and $P$ intersects $E$ at exactly three points, then the eccentricity of $E$ is equal to
Given the length of the latus rectum of the parabola $l=2 p=2 c=4 b \Rightarrow c^{2}=4 b^{2}=4\left(a^{2}-c^{2}\right) \Rightarrow e=\frac{2 \sqrt{5}}{5}$.